Researcher Database

Kimura Masaaki
Faculty of Science Physics Nonlinear Physics
Professor

Researcher Profile and Settings

Affiliation

  • Faculty of Science Physics Nonlinear Physics

Job Title

  • Professor

Degree

  • Ph.D(Kyoto University)

J-Global ID

Research Interests

  • 原子核理論   クラスター   元素合成   不安定核   

Research Areas

  • Natural sciences / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics

Academic & Professional Experience

  • 2020/04 - Today Hokkaido University Faculty of Science Professor
  • 2012/04 - Today Hokkaido University Faculty of Science Associate Professor
  • 2008/02 - 2011/12 Hokkaido University Sousei Research Institute Assistant
  • 2006/04 - 2008/01 JSPS Special Research Fellow(PD), Tsukuba University
  • 2005/04 - 2006/03 Kyoto University Yukawa Institute for Theoretical Physics Research Fellow
  • 2002/04 - 2005/03 RIKEN Nishina Center Special Postdoctral Researcher

Education

  • 1997/04 - 2002/03  Kyoto University  Graduate School of Science
  • 1993/04 - 1997/03  Kyoto University  Faculty of Science

Research Activities

Published Papers

  • H. Nishibata, K. Tajiri, T. Shimoda, A. Odahara, S. Morimoto, S. Kanaya, A. Yagi, H. Kanaoka, M. R. Pearson, C. D. P. Levy, M. Kimura, N. Tsunoda, T. Otsuka
    Physical Review C 102 (5) 2469-9985 2020/11/25 [Refereed]
  • Bo Zhou, Masaaki Kimura, Qing Zhao, Seung-heon Shin
    The European Physical Journal A 56 (11) 1434-6001 2020/11
  • V. Choudhary, W. Horiuchi, M. Kimura, R. Chatterjee
    Physical Review C 102 (3) 2469-9985 2020/09/29 [Refereed]
  • Masaaki Kimura, Yasutaka Taniguchi
    Physical Review C 102 (2) 2469-9985 2020/08/19 [Refereed]
  • T. Baba, M. Kimura
    Physical Review C 102 (2) 2469-9985 2020/08/14 [Refereed]
  • Y. Liu, Y. L. Ye, J. L. Lou, X. F. Yang, T. Baba, M. Kimura, B. Yang, Z. H. Li, Q. T. Li, J. Y. Xu, Y. C. Ge, H. Hua, J. S. Wang, Y. Y. Yang, P. Ma, Z. Bai, Q. Hu, W. Liu, K. Ma, L. C. Tao, Y. Jiang, L. Y. Hu, H. L. Zang, J. Feng, H. Y. Wu, J. X. Han, S. W. Bai, G. Li, H. Z. Yu, S. W. Huang, Z. Q. Chen, X. H. Sun, J. J. Li, Z. W. Tan, Z. H. Gao, F. F. Duan, J. H. Tan, S. Q. Sun, Y. S. Song
    Physical Review Letters 124 (19) 0031-9007 2020/05/12 [Refereed]
  • H. Masui, W. Horiuchi, M. Kimura
    Physical Review C 101 (4) 2469-9985 2020/04/10 [Refereed]
  • Y. Chiba, M. Kimura
    Physical Review C 101 (2) 2469-9985 2020/02/28 [Refereed]
  • Taniguchi, Yasutaka, Kimura, Masaaki
    PHYSICS LETTERS B 800 0370-2693 2020/01 [Refereed][Not invited]
     
    The existence of C-12 + O-16 molecular resonances at sub-barrier energy has been a significant problem in nuclear astrophysics because they strongly affect the C-12 + O-16 fusion reaction rate in type Ia supernovae and heavy stars. However, experimental surveys have been limited to 4 MeV and cannot access the deep sub-barrier energy due to a very small fusion cross section. Here we predict a couple of resonances with J(pi) = 0(+), 2(+), and 4(+) in the deep sub-barrier energy based on the antisymmetrized molecular dynamics calculation that reproduces the known resonances and low-lying spectrum of Si-28. (C) 2019 The Author(s). Published by Elsevier B.V.
  • T. Baba, M. Kimura
    Physical Review C 100 (6) 2469-9985 2019/12/18 [Refereed]
  • Quantitative description of the 20Ne(p,pα)16O cross section for probing the surface alpha amplitude
    K. Yoshida, Y. Chiba, M. Kimura, Y. Taniguchi, Y. Kanada-En'yo, K. Ogata
    Physical Review C 2019/10 [Refereed][Not invited]
  • Yoshida, Kazuki, Chiba, Yohei, Kimura, Masaaki, Taniguchi, Yasutaka, Kanada-En'yo, Yoshiko, Ogata, Kazuyuki
    PHYSICAL REVIEW C 100 (4) 2469-9985 2019/10 [Refereed][Not invited]
     
    Background: The proton-induced alpha knockout reaction has been utilized for decades to investigate the alpha cluster formation in the ground state of nucleus. However, even today, the theoretical description of the reaction is not precise enough for the quantitative study. For example, the alpha spectroscopic factors reduced from alpha knockout experiments with reaction analyses using phenomenological alpha cluster wave functions disagree with those given by a structure theory. In some cases they also scatter depending on the kinematical condition of the experiment. This suggests that the theoretical description of the alpha knockout reaction is insufficient from a quantitative viewpoint.Purpose: We show that the distorted wave impulse approximation can describe Ne-20(p, p alpha)O-16 reaction quantitatively if reliable inputs are used; the optical potential, the p-alpha cross section, and the alpha cluster wave function. We also investigate the relationship between the alpha cluster wave function and the alpha knockout cross section.Method: The Ne-20(p, p alpha)O-16 reaction is described by the distorted wave impulse approximation. An input of the calculation, the alpha-O-16 cluster wave function, is obtained by the antisymmetrized molecular dynamics and the Laplace expansion method.Results: In contrast to the previous work, the Ne-20(p, p alpha)O-16 data at 101.5 MeV is successfully reproduced by the present framework without any free adjustable parameters. It is also found that the knockout cross section is sensitive to the surface region of the cluster wave function because of the peripherality of the reaction.Conclusions: Using a reliable alpha cluster wave function, p-alpha cross section, and distorting potentials, it is found that the Ne-20(p, p alpha)O-16 cross section is quantitatively reproduced by the present framework. This success demonstrates that the proton-induced alpha knockout reaction is a quantitative probe for the alpha clustering.
  • R. Imai, T. Tada, M. Kimura
    Physical Review C 99 (6) 2469-9985 2019/06/24 [Refereed]
  • Bo Zhou, Yasuro Funaki, Hisashi Horiuchi, Masaaki Kimura, Zhongzhou Ren, Gerd Röpke, Peter Schuck, Akihiro Tohsaki, Chang Xu, Taiichi Yamada
    Physical Review C 99 (5) 2469-9985 2019/05/21 [Refereed]
  • H. Nishibata, S. Kanaya, T. Shimoda, A. Odahara, S. Morimoto, A. Yagi, H. Kanaoka, M. R. Pearson, C. D. P. Levy, M. Kimura, N. Tsunoda, T. Otsuka
    Physical Review C 99 (2) 2469-9985 2019/02/26 [Refereed]
  • T. Baba, M. Kimura
    Physical Review C 99 (2) 2469-9985 2019/02/13 [Refereed]
  • Bo Zhou, Masaaki Kimura
    Physical Review C 98 (5) 2469-9985 2018/11/29 [Refereed]
  • T. Baba, M. Kimura
    Physical Review C 97 (5) 2469-9985 2018/05/14 [Refereed][Not invited]
     
    The linear-chain states of C16 and their decay modes are theoretically investigated by using the antisymmetrized molecular dynamics. It is found that the positive-parity linear-chain states have the (3/2π-)2(1/2σ-)2 configuration and primary decay to Be12(21+) as well as to Be12(g.s.) by α-particle emission. Moreover, we show that they also decay via the He6+Be10 channel. In the negative-parity states, it is found that two types of linear chains exist. One has the valence neutrons occupying the molecular orbits (3/2π-)2(1/2σ-)(3/2π+), while the other's configuration cannot be explained in terms of the molecular orbits because of the strong parity mixing. Both configurations constitute the rotational bands with a large moment of inertia and intraband E2 transitions. Their α and He6 reduced widths are sufficiently large to be distinguished from other noncluster states although they are smaller than those of the positive-parity linear chain.
  • S. Momiyama, P. Doornenbal, H. Scheit, S. Takeuchi, M. Niikura, N. Aoi, K. Li, M. Matsushita, D. Steppenbeck, H. Wang, H. Baba, E. Ideguchi, M. Kimura, N. Kobayashi, Y. Kondo, J. Lee, S. Michimasa, T. Motobayashi, N. Shimizu, M. Takechi, Y. Togano, Y. Utsuno, K. Yoneda, H. Sakurai
    PHYSICAL REVIEW C 96 (3) 2469-9985 2017/09 [Refereed][Not invited]
     
    The isotope Mg-35 was spectroscopically studied via nucleon-removal reactions from Mg-36 and Al-37 secondary beams at intermediate energies. The experiment's aim was to clarify the level structure of this nucleus located in between the N = 20 and 28 shell quenchings. De-excitation gamma-ray energies, exclusive cross sections, and parallel momentum of outgoing Mg-35 for several final states were measured and compared to structure calculations in the shell model and antisymmetrized molecular dynamics framework and the eikonal reaction calculation, further developing the level scheme of Mg-35. It was found that a large fraction of the one-neutron knockout reaction goes into unbound states of Mg-35, which may explain missing f-wave strength.
  • T. Baba, M. Kimura
    PHYSICAL REVIEW C 95 (6) 2469-9985 2017/06 [Refereed][Not invited]
     
    The decay properties of the linear-chain states in C-14 are investigated by using antisymmetrized molecular dynamics. The calculation predicts two rotational bands with linear-chain configurations having the pi-bond and sigma-bond valence neutrons. For the pi-bond linear-chain, the calculated excitation energies and the widths of alpha-decay to the ground state of Be-10 reasonably agree with the experimental candidates observed by the alpha + Be-10 resonant scattering. On the other hand, the sigma-bond linear-chain is the candidate of the higher-lying resonant states reported by the breakup reaction. As the evidence of the sigma-bond linear chain, we discuss its decay pattern. It is found that the sigma-bond linear chain not only decays to the excited band of Be-10 but also decays to the three-body channel of He-6 + alpha + alpha, and the branching ratio of these decays are comparable. Hence, we suggest that this characteristic decay pattern is a strong signature of the linear-chain formation and a key observable to distinguish two different linear chains.
  • Yohei Chiba, Masaaki Kimura
    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS (5) 2050-3911 2017/05 [Refereed][Not invited]
     
    We derive the equations to calculate the reduced-width amplitudes (RWAs) of unequal-sized clusters and deformed clusters without any approximation. These equations, named the Laplace expansion method, are applicable to nuclear models that use Gaussian wave packets. The advantage of the method is demonstrated by numerical calculations of the O-16 + alpha and Mg-24 + alpha RWAs in Ne-20 and Si-28.
  • H. Nishibata, T. Shimoda, A. Odahara, S. Morimoto, S. Kanaya, A. Yagi, H. Kanaoka, M. R. Pearson, C. D. P. Levy, M. Kimura
    PHYSICS LETTERS B 767 81 - 85 0370-2693 2017/04 [Refereed][Not invited]
     
    The structure of excited states in the neutron-rich nucleus Mg-31, which is in the region of the "island of inversion" associated with the neutron magic number N=20, is studied by beta-gamma spectroscopy of spin-polarized Na-31. Among the Mg-31 levels below the one neutron separation energy of 2.3MeV, the spin values of all five positive-parity levels are unambiguously determined by observing the anisotropic beta decay. Two rotational bands with K-pi = 1/2(+) and 1/2(-) are proposed based on the spins and energies of the levels. Comparison on a level-by-level basis is performed between the experimental results and theoretical calculations by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM). It is found that various nuclear structures coexist in the low excitation energy region in Mg-31. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license.
  • Y. Chiba, Y. Taniguchi, M. Kimura
    PHYSICAL REVIEW C 95 (4) 2469-9985 2017/04 [Refereed][Not invited]
     
    Background: Various cluster states of astrophysical interest are expected to exist in the excited states of Si-28. However, they have not been identified firmly, because of the experimental and theoretical difficulties. Purpose: To establish the Mg-24 + alpha, O-16 + C-12, and Ne-20 + 2 alpha cluster bands, we theoretically search for the negative-parity cluster bands that are paired with the positive-parity bands to constitute the inversion doublets. We also offer the isoscalar monopole and dipole transitions as a promising probe for the clustering. We numerically show that these transition strengths from the ground state to the cluster states are very much enhanced. Method: The antisymmetrized molecular dynamics with GognyD1S effective interaction is employed to calculate the excited states of Si-28. The isoscalar monopole and dipole transition strengths are directly evaluated from wave functions of the ground and excited states. Results: Negative-parity bands having Mg-24 + alpha and O-16 + C-12 cluster configurations are obtained in addition to the newly calculated Ne-20 + 2 alpha cluster bands. All of them are paired with the corresponding positive-parity bands to constitute the inversion doublets with various cluster configurations. The calculation shows that the bandheads of the Mg-24 + alpha and Ne-20 + 2 alpha cluster bands are strongly excited by the isoscalar monopole and dipole transitions. Conclusions: The present calculation suggests the existence of inversion doublets with the Mg-24 + alpha, O-16 + C-12, and Ne-20 + 2 alpha configurations. Because of the enhanced transition strengths, we offer the isoscalar monopole and dipole transitions as good probe for the Mg-24 + alpha and Ne-20 + 2 alpha cluster bands.
  • M. Kimura
    PHYSICAL REVIEW C 95 (3) 2469-9985 2017/03 [Refereed][Not invited]
     
    The low-lying spectra of Ne-24,Ne-25,Ne-26 and the structure of the pygmy dipole resonance (PDR) in Ne-26 have been theoretically studied by the antisymmetrized molecular dynamics (AMD) and its extended version called shifted-basis AMD. The calculated energy and strength of the PDR reasonably agree with the observation, and the analysis of the wave function shows that the PDR is dominated by neutron excitation coupled to the quadrupole excited core nucleus Ne-25, which explains the observed unexpected decay of PDR to the excited states of Ne-25. The large isoscalar component of PDR is also shown and the enhancement of the core excitation in neutron-rich Ne isotopes is conjectured.
  • M. Kimura, T. Suhara, Y. Kanada-En'yo
    EUROPEAN PHYSICAL JOURNAL A 52 (12) 1434-6001 2016/12 [Refereed][Not invited]
     
    We present a review of recent works on clustering phenomena in unstable nuclei studied by antisymmetrized molecular dynamics (AMD). The AMD studies in these decades have uncovered novel types of clustering phenomena brought about by the excess neutrons. Among them, this review focuses on the molecule-like structure of unstable nuclei. One of the earliest discussions on the clustering in unstable nuclei was made for neutron-rich Be and B isotopes. AMD calculations predicted that the ground state clustering is enhanced or reduced depending on the number of excess neutrons. Today, the experiments are confirming this prediction as the change of the proton radii. Behind this enhancement and reduction of the clustering, there are underlying shell effects called molecular and atomic orbits. These orbits form covalent and ionic bonding of the clusters analogous to the atomic molecules. It was found that this "molecular-orbit picture" reasonably explains the low-lying spectra of Be isotopes. The molecular-orbit picture is extended to other systems having parity asymmetric cluster cores and to the three cluster systems. O and Ne isotopes are the candidates of the former, while the 3 alpha linear chains in C isotopes are the latter. For both subjects, many intensive studies are now in progress. We also pay a special attention to the observables which are the fingerprint of the clustering. In particular, we focus on the monopole and dipole transitions which are recently regarded as good probe for the clustering. We discuss how they have and will reveal the exotic clustering.
  • T. Baba, M. Kimura
    PHYSICAL REVIEW C 94 (4) 2469-9985 2016/10 [Refereed][Not invited]
     
    The linear-chain states of C-14 are theoretically investigated by using the antisymmetrized molecular dynamics. The calculated excitation energies and the alpha decay widths of the linear-chain states were compared with the observed data reported by recent experiments. The properties of the positive-parity linear-chain states reasonably agree with the observation, which convinces us of the linear-chain formation in the positive-parity states. On the other hand, in the negative-parity states, it is found that the linear-chain configuration does not correspond to a single eigenstate but is mixed with other configurations in the eigenstates and does not form a single rotational band. As a further evidence of the linear-chain formation, we focus on the alpha-decay pattern. It is shown that the linear-chain states decay to the excited states of daughter nucleus Be-10 as well as to the ground state, while other cluster states dominantly decay into the ground state. Hence, we regard that this characteristic decay pattern is a strong signature of linear-chain formation.
  • R. Kanungo, W. Horiuchi, G. Hagen, G. R. Jansen, P. Navratil, F. Ameil, J. Atkinson, Y. Ayyad, D. Cortina-Gil, I. Dillmann, A. Estrade, A. Evdokimov, F. Farinon, H. Geissel, G. Guastalla, R. Janik, M. Kimura, R. Knoebel, J. Kurcewicz, Yu. A. Litvinov, M. Marta, M. Mostazo, I. Mukha, C. Nociforo, H. J. Ong, S. Pietri, A. Prochazka, C. Scheidenberger, B. Sitar, P. Strmen, Y. Suzuki, M. Takechi, J. Tanaka, I. Tanihata, S. Terashima, J. Vargas, H. Weick, J. S. Winfield
    PHYSICAL REVIEW LETTERS 117 (10) 0031-9007 2016/09 [Refereed][Not invited]
     
    Proton radii of C12-19 densities derived from first accurate charge changing cross section measurements at 900A MeV with a carbon target are reported. A thick neutron surface evolves from similar to 0.5 fm in C-15 to similar to 1 fm in C-19. The halo radius in C-19 is found to be 6.4 +/- 0.7 fm as large as Li-11. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.
  • J. Lee, H. Liu, P. Doornenbal, M. Kimura, K. Minomo, K. Ogata, Y. Utsuno, N. Aoi, K. Li, M. Matsushita, H. Scheit, D. Steppenbeck, S. Takeuchi, H. Wang, H. Baba, E. Ideguchi, N. Kobayashi, Y. Kondo, S. Michimasa, T. Motobayashi, H. Sakurai, M. Takechi, Y. Togano
    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS (8) 2050-3911 2016/08 [Refereed][Not invited]
     
    The single-neutron and -proton removal reactions of Ne-30 with large separation-energy asymmetry vertical bar Delta S vertical bar = vertical bar S-n - S-p vertical bar at incident energies of about 230 MeV/nucleon are measured. In the case of the deeply bound nucleon removal data, a large disagreement is obtained from the theoretical cross sections calculated using the eikonal reaction theory, with nuclear structure inputs from the many-body shell-model theory and the antisymmetrized molecular dynamics theory, respectively. Such a discrepancy is consistent with the systematics observed from the knockout reactions at incident energies similar to 100 MeV/nucleon.
  • Hiroshi Masui, Masaaki Kimura
    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS (5) 2050-3911 2016/05 [Refereed][Not invited]
     
    We study the deuteron-like correlation (T = 0) in F-18 using the cluster-orbital shell model approach within the core+ p + n model space, which successfully reproduces the observed properties of F-18 such as B(M1) and the matter radius. Based on the analysis of the correlation energy, magnetic moment, and opening angle, it is found that the deuteron-like proton-neutron pair is formed despite the deep binding of the valence nucleons. It is shown that the [j > circle times j <](T=0)(J=1) configurations play an important role because of the deuteron-like pair formation. We show that the strong correlation leads to the non-negligible occupation of p f and higher shells that are embedded in the single-particle continua, and gives rise to the spatially correlated deuteron-like pair formation. We also investigate how the spin-orbit interaction affects the correlation energy, because the occupation probability of the [j >.circle times j <](T=0)(J=1) configurations strongly depends on the spin-orbit splitting.
  • Y. Chiba, M. Kimura, Y. Taniguchi
    PHYSICAL REVIEW C 93 (3) 2469-9985 2016/03 [Refereed][Not invited]
     
    Background: The sharp 1(-) resonances with enhanced isoscalar dipole transition strengths are observed in many light nuclei at relatively small excitation energies, but their nature has been unclear. Purpose: We show those resonances can be attributed to the cluster states with asymmetric configurations such as alpha + O-16. We explain why asymmetric cluster states are strongly excited by the isoscalar dipole transition. We also provide a theoretical prediction of the isoscalar dipole transitions in Ne-20 and Ti-44. Method: The transition matrix is analytically derived to clarify the excitation mechanism. The nuclear model calculations by Brink-Bloch wave function and antisymmetrized molecular dynamics are also performed to provide a theoretical prediction for Ne-20 and Ti-44. Results: It is shown that the transition matrix is as large as the Weisskopf estimate even though the ground state is an ideal shell-model state. Furthermore, it is considerably amplified if the ground state has cluster correlation. The nuclear model calculations predict large transition matrix to the a + O-16 and a + Ca-40 cluster states comparable with or larger than the Weisskopf estimate. Conclusions: We conclude that the asymmetric cluster states are strongly excited by the isoscalar dipole transition. Combined with the isoscalar monopole transition that populates the 0(+) cluster states, the isoscalar transitions are promising probes for asymmetric clusters.
  • Masahiro Isaka, Masaaki Kimura, Emiko Hiyama, Hiroyuki Sagawa
    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS (10) 2050-3911 2015/10 [Refereed][Not invited]
     
    We investigate the differences in the Lambda separation energies (S-Lambda) of the ground and superdeformed (SD) states in (37)(Lambda) Ar, (39)(Lambda) Ar, and (41)(Lambda) Ar within the framework of antisymmetrized molecular dynamics (AMD). In this study, we find that the calculated S-Lambda values in the SD states are much smaller than those in the ground states, unlike the result using the relativistic mean-field (RMF) calculation [ B.-N. Lu et al., Phys. Rev. C, 89, 044307 (2014)]. One of the reasons for this difference between the present work and the RMF calculation is the difference in the density profile of the SD states in the core nuclei. We also find that the property of the Lambda N odd-parity interaction affects the S-Lambda trend between the ground and SD states.
  • M. Isaka, M. Kimura
    PHYSICAL REVIEW C 92 (4) 0556-2813 2015/10 [Refereed][Not invited]
     
    The low-lying structures of Be-10(Lambda) and Be-11(Lambda) are investigated within the framework of the antisymmetrized molecular dynamics. We focus on the modifications of the excitation spectra and dynamical changes of the 2 alpha cluster structure caused by a Lambda particle as an impurity in these hypernuclei. It is found that the excitation energies of well-pronounced cluster states are largely shifted up by the addition of a Lambda particle. Furthermore, we also find that the 2 alpha cluster structure is significantly changed in the excited states, whereas it is almost unchanged in the ground states.
  • Y. Chiba, M. Kimura
    PHYSICAL REVIEW C 91 (6) 0556-2813 2015/06 [Refereed][Not invited]
     
    Background: Isoscalar monopole transition has been suggested as a key observable to search for exotic cluster states. Recently, excited 0(+) states with strong isoscalar monopole transition strengths were experimentally reported in Mg-24, but their structures were not revealed because of the lack of theoretical analysis. Purpose: We study the structure of the excited 0(+) states of Mg-24 populated by isoscalar monopole transition from the ground state, and identify their cluster configurations. Method: The 0(+) states of Mg-24 and their isoscalar monopole transition strengths from the ground state are calculated with antisymmetrized molecular dynamics combined with the generator coordinate method using the Gogny D1S interaction. Results: The calculated isoscalar monopole strength function shows reasonable agreement with experiment and is consistent with other theoretical calculations. The structures of the excited 0(+) states with pronounced isoscalar monopole transitions are analyzed. It is found that the 0(2)(+), 0(3)(+), and 0(5)(+) states have mixed nature of mean-field and cluster, and that the 0(8)(+) state is dominated by a C-12 + C-12 cluster configuration. In addition, it is predicted that 5 alpha-pentagon + alpha states appear around 23 MeV. Conclusions: The excited 0(+) states which appear as the prominent peaks in the calculated strength function are associated with Ne-20 + alpha, C-12 + C-12, and 5 alpha-pentagon+alpha cluster states.
  • Yoshiko Kanada-En'yo, Masaaki Kimura, Fumiharu Kobayashi, Tadahiro Suhara, Yasutaka Taniguchi, Yuta Yoshida
    NUCLEAR SCIENCE AND TECHNIQUES 26 (2) 1001-8042 2015/04 [Refereed][Not invited]
     
    Cluster structures in light unstable nuclei are discussed. The structures of neutron-rich Be isotopes are theoretically investigated and the molecular orbital bond structure and its role in the vanishing of the neutron magic number N = 8 are discussed. The two-body cluster resonances in highly excited states of neutron-rich Li, Be and B isotopes are predicted theoretically.
  • H. Homma, M. Isaka, M. Kimura
    Physical Review C - Nuclear Physics 91 (1) 1089-490X 2015/01/16 [Refereed][Not invited]
     
    We study the spectrum of Λ12Be by using an extended version of antisymmetrized molecular dynamics for hypernuclei. Our result indicates that the Λ-particle impurity effect causes the positive-parity ground state of Λ12Be to revert to the normal state, i.e. negative parity. This parity reversion is attributed to the difference in the Λ binding energy between the positive- and negative-parity states, which in turn originates in the difference in α clustering and deformation.
  • Shuichiro Ebata, Masaaki Kimura
    PHYSICAL REVIEW C 91 (1) 0556-2813 2015/01 [Refereed][Not invited]
     
    The quadrupole vibrational modes of neutron-rich N = 28 isotones (Ca-48, Ar-46, S-44, and Si-42) are investigated by using the canonical-basis time-dependent Hartree-Fock-Bogoliubov theory with several choice of energy density functionals, including nuclear pairing correlation. It is found that the quenching of the N = 28 shell gap and the proton holes in the sd shell trigger quadrupole correlation and increase the collectivity of the low-lying 2(+) state in Ar-46. It is also found that the pairing correlation plays an important role to increase the collectivity. We also demonstrate that the same mechanism to enhance the low-lying collectivity applies to other N = 28 isotones S-44 and Si-42, and it generates a couple of low-lying 2(+) states which can be associated with the observed 2(+) states.
  • H. Homma, M. Isaka, M. Kimura
    PHYSICAL REVIEW C 91 (1) 2469-9985 2015/01 [Refereed][Not invited]
     
    We study the spectrum of Be-12(Lambda) by using an extended version of antisymmetrized molecular dynamics for hypernuclei. Our result indicates that the Lambda-particle impurity effect causes the positive-parity ground state of Be-12(Lambda) to revert to the normal state, i.e., negative parity. This parity reversion is attributed to the difference in the Lambda binding energy between the positive- and negative-parity states, which in turn originates in the difference in alpha clustering and deformation.
  • T. Baba, Y. Chiba, M. Kimura
    Physical Review C - Nuclear Physics 90 (6) 1089-490X 2014/12/29 [Refereed][Not invited]
     
    The α-cluster states of C16 are investigated by using antisymmetrized molecular dynamics. It is shown that two different types of α-cluster states exist: triangular and linear-chain states. The former has an approximate isosceles triangular configuration of α particles surrounded by four valence neutrons occupying the sd shell, while the latter has the linearly aligned α particles with (sd)2(pf)2 neutrons. It is found that the structure of the linear-chain state is qualitatively understood in terms of the 3/2π- and 1/2σ- molecular orbits as predicted by molecular-orbital model, but there exists a non-negligible Be10+α+2n correlation. The bandhead energies of the triangular and linear-chain rotational bands are 8.0 and 15.5 MeV, and the latter is close to the He4+Be12 and He6+Be10 threshold energies. It is also shown that the linear-chain state becomes the yrast state at Jπ=10+ with Ex=27.8 MeV owing to its very large moment of inertia comparable with hyperdeformation.
  • M. Takechi, S. Suzuki, D. Nishimura, M. Fukuda, T. Ohtsubo, M. Nagashima, T. Suzuki, T. Yamaguchi, A. Ozawa, T. Moriguchi, H. Ohishi, T. Sumikama, H. Geissel, N. Aoi, Rui-Jiu Chen, De-Qing Fang, N. Fukuda, S. Fukuoka, H. Furuki, N. Inabe, Y. Ishibashi, T. Itoh, T. Izumikawa, D. Kameda, T. Kubo, M. Lantz, C. S. Lee, Yu-Gang Ma, K. Matsuta, M. Mihara, S. Momota, D. Nagae, R. Nishikiori, T. Niwa, T. Ohnishi, K. Okumura, M. Ohtake, T. Ogura, H. Sakurai, K. Sato, Y. Shimbara, H. Suzuki, H. Takeda, S. Takeuchi, K. Tanaka, M. Tanaka, H. Uenishi, M. Winkler, Y. Yanagisawa, S. Watanabe, K. Minomo, S. Tagami, M. Shimada, M. Kimura, T. Matsumoto, Y. R. Shimizu, M. Yahiro
    PHYSICAL REVIEW C 90 (6) 0556-2813 2014/12 [Refereed][Not invited]
     
    Precise reaction cross sections (sigma R) for (24- 38) Mg on C targets at energies around 240 MeV/nucleon have been measured at the Radioactive Isotope Beam Factory at RIKEN. The sigma R for (36-38) Mg have been measured for the first time. An enhancement of sR compared to the systematics for spherical stable nuclei has been observed, especially in the neutron-rich region, which reflects the deformation of those isotopes. In the vicinity of the drip line the sR for Mg-37 is especially large. It is shown by analysis using a recently developed theoretical method that this prominent enhancement of sR for Mg-37 should come from the p-orbital halo formation breaking the N = 28 shell gap.
  • T. Baba, Y. Chiba, M. Kimura
    PHYSICAL REVIEW C 90 (6) 2469-9985 2014/12 [Refereed][Not invited]
     
    The alpha-cluster states of C-16 are investigated by using antisymmetrized molecular dynamics. It is shown that two different types of alpha-cluster states exist: triangular and linear-chain states. The former has an approximate isosceles triangular configuration of a particles surrounded by four valence neutrons occupying the sd shell, while the latter has the linearly aligned a particles with (sd)(2)(pf)(2) neutrons. It is found that the structure of the linear-chain state is qualitatively understood in terms of the 3/2(pi)(-) and 1/ 2(sigma)(-) molecular orbits as predicted by molecular-orbital model, but there exists a non-negligible Be-10 + alpha + 2n correlation. The bandhead energies of the triangular and linear-chain rotational bands are 8.0 and 15.5 MeV, and the latter is close to the He-4 + Be-12 and He-6 + 10Be threshold energies. It is also shown that the linear-chain state becomes the yrast state at J(pi) = 10(+) with E-x = 27.8 MeV owing to its very large moment of inertia comparable with hyperdeformation.
  • S. Terashima, I. Tanihata, R. Kanungo, A. Estrade, W. Horiuchi, F. Ameil, J. Atkinson, Y. Ayyad, D. Cortina-Gil, I. Dillmann, A. Evdokimov, F. Farinon, H. Geissel, G. Guastalla, R. Janik, M. Kimura, R. Knoebel, J. Kurcewicz, Yu. A. Litvinov, M. Marta, M. Mostazo, I. Mukha, T. Neff, C. Nociforo, H. J. Ong, S. Pietri, A. Prochazka, C. Scheidenberger, B. Sitar, Y. Suzuki, M. Takechi, J. Tanaka, J. Vargas, J. S. Winfield, H. Weick
    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS (10) 2050-3911 2014/10 [Refereed][Not invited]
     
    The charge-changing cross sections of Be-7,Be-9-12,Be-14 have been measured at 900A MeV on a carbon target. These cross sections are discussed both in terms of a geometrical and a Glauber model. From several different analyses of the cross sections, the proton distribution radius (proton radius) of Be-14 is determined for the first time to be 2.41 +/- 0.04 fm. A large difference in the proton and neutron radii is found. The proton radii are compared to the results of fermionic molecular dynamics (FMD) and antisymmetrized molecular dynamics (AMD) calculations.
  • A. Estrade, R. Kanungo, W. Horiuchi, F. Ameil, J. Atkinson, Y. Ayyad, D. Cortina-Gil, I. Dillmann, A. Evdokimov, F. Farinon, H. Geissel, G. Guastalla, R. Janik, M. Kimura, R. Knoebel, J. Kurcewicz, Yu. A. Litvinov, M. Marta, M. Mostazo, I. Mukha, C. Nociforo, H. J. Ong, S. Pietri, A. Prochazka, C. Scheidenberger, B. Sitar, P. Strmen, Y. Suzuki, M. Takechi, J. Tanaka, I. Tanihata, S. Terashima, J. Vargas, H. Weick, J. S. Winfield
    PHYSICAL REVIEW LETTERS 113 (13) 0031-9007 2014/09 [Refereed][Not invited]
     
    The first determination of radii of point proton distribution (proton radii) of B12-17 from charge-changing cross sections (sigma(CC)) measurements at the FRS, GSI, Darmstadt is reported. The proton radii are deduced from a finite-range Glauber model analysis of the sCC. The radii show an increase from B-13 to B-17 and are consistent with predictions from the antisymmetrized molecular dynamics model for the neutron-rich nuclei. The measurements show the existence of a thick neutron surface with neutron-proton radius difference of 0.51(0.11) fm in B-17.
  • Y. Chiba, M. Kimura
    PHYSICAL REVIEW C 89 (5) 0556-2813 2014/05 [Refereed][Not invited]
     
    The positive-parity excited states of Ni-56 and instability of the N = Z = 28 shell gap are discussed on the basis of the antisymmetrized molecular dynamics calculation using the Gogny D1S effective interaction. It is found that Ni-56 is quite soft against oblate deformation and the N = Z = 28 closed-shell configuration amounts to only 62% in the ground state. It is also found that the shell gap easily disappears by prolate deformation, which leads to the coexistence of the almost spherical ground band, excited beta and gamma bands, and a prolate superdeformed band with (f(7/2))(-m)(p(3/2))(m) configurations within the small excitation energies. Furthermore, in the highly excited region, it is predicted that a couple of strongly deformed bands with (sd)(-m)(pf)(-n)(g(9/2))(m+n) configurations are built on the 0(+) states around 20 MeV.
  • S. Watanabe, K. Minomo, M. Shimada, S. Tagami, M. Kimura, M. Takechi, M. Fukuda, D. Nishimura, T. Suzuki, T. Matsumoto, Y. R. Shimizu, M. Yahiro
    PHYSICAL REVIEW C 89 (4) 0556-2813 2014/04 [Refereed][Not invited]
     
    We analyze recently measured total reaction cross sections for Mg24-38 isotopes incident on C-12 targets at 240 MeV/nucleon by using the folding model and antisymmetrized molecular dynamics (AMD). The folding model well reproduces the measured reaction cross sections, when the projectile densities are evaluated by the deformed Woods-Saxon (def-WS) model with AMD deformation. Matter radii of Mg24-38 are then deduced from the measured reaction cross sections by fine tuning the parameters of the def-WS model. The deduced matter radii are largely enhanced by nuclear deformation. Fully microscopic AMD calculations with no free parameter well reproduce the deduced matter radii for Mg24-36, but still considerably underestimate them for Mg-37,Mg-38. The large matter radii suggest that Mg-37,Mg-38 are candidates for deformed halo nucleus. AMD also reproduces other existing measured ground-state properties (spin parity, total binding energy, and one-neutron separation energy) of Mg isotopes. Neutron-number (N) dependence of deformation parameter is predicted by AMD. Large deformation is seen from Mg-31 with N = 19 to a drip-line nucleus Mg-40 with N = 28, indicating that both the N = 20 and 28 magicities disappear. N dependence of neutron skin thickness is also predicted by AMD.
  • M. Isaka, K. Fukukawa, M. Kimura, E. Hiyama, H. Sagawa, Y. Yamamoto
    PHYSICAL REVIEW C 89 (2) 0556-2813 2014/02 [Refereed][Not invited]
     
    The response to the addition of a Lambda hyperon is investigated for the deformed states such as superdeformation in Ca-41(Lambda), Sc-46(Lambda), and Sc-48(Lambda). In the present study, we use the antisymmetrized molecular dynamics model. It is pointed out that many kinds of deformed bands appear in Sc-45 and Sc-47. Especially, it is found that there exists superdeformed states in Sc-45. By the addition of a Lambda particle to Ca-40, Sc-45, and Sc-47, it is predicted, for the first time, that the superdeformed states exist in the hypernuclei Ca-41(Lambda) and Sc-46(Lambda). The manifestation of the dependence of the Lambda-separation energy on nuclear deformation such as spherical, normal deformation, and superdeformation is shown in the energy spectra of Ca-41(Lambda), Sc-46(Lambda), and Sc-48(Lambda) hypernuclei.
  • Masahiro Isaka, Masaaki Kimura, Akinobu Dote, Akira Ohnishi
    NUCLEAR PHYSICS A 914 189 - 193 0375-9474 2013/09 [Refereed][Not invited]
     
    The excited states of Mg-25(Lambda) with the A hyperon in p-orbit are studied with the antisymmetrized molecular dynamics for hypernuclei. Three rotational bands are obtained by adding a Lambda in a p-orbit to the ground band of Mg-24. It is found that these bands energetically split due to the triaxial deformation of the core nucleus Mg-24 and the spatial anisotropy of the p-orbits of Lambda. (C) 2013 Elsevier B.V. All rights reserved.
  • Masahiro Isaka, Hiroaki Homma, Masaaki Kimura, Akinobu Dote, Akira Ohnishi
    FEW-BODY SYSTEMS 54 (7-10) 1219 - 1222 0177-7963 2013/08 [Refereed][Not invited]
     
    The low-lying level structure of and has been studied by using the antisymmetrized molecular dynamics for hypernuclei (HyperAMD). In these hypernuclei, it is interesting to reveal the changes of excitation spectra by adding I > hyperon, because the ground and low-lying states with different deformation coexist in Be-9 and Be-11. Based on the HyperAMD calculation, it is found that the first excited state 1/2(+) of Be-9 is shifted up by about 700 keV in . In , the parity-inverted ground state of Be-11 is reverted by adding I > hyperon. In this article, we discuss the reason for these structure changes related to the coexistence of ground and low-lying states with different deformation.
  • Masahiro Isaka, Hiroaki Homma, Masaaki Kimura, Akinobu Dote, Akira Ohnishi
    FEW-BODY SYSTEMS 54 (1-4) 395 - 398 0177-7963 2013/03 [Refereed][Not invited]
     
    The deformation change of Be and the low-lying states of Be are studied by using the antisymmetrized molecular dynamics for hypernuclei (HyperAMD). In Be, the I > hyperon in p orbit enhances nuclear quadrupole deformation, while the I > hyperon in s orbit reduces it. In Be, the ground state parity inverted in Be-11 is reverted in Be by adding a I > hyperon as an impurity (impurity effect).
  • Masahiro Isaka, Masaaki Kimura, Akinobu Dote, Akira Ohnishi
    PHYSICAL REVIEW C 87 (2) 0556-2813 2013/02 [Refereed][Not invited]
     
    The excited states of Mg-25(A) with the A hyperon in p orbit are studied within the framework of the antisymmetrized molecular dynamics for hypernuclei. We obtained five rotational bands in (AMgMg)-Mg-25 in which the A hyperon in p orbit is coupled to the ground and K-pi = 2(+) bands of Mg-24. We predict that the corresponding bands of Mg-25(A) energetically split due to the triaxial deformation of the core nucleus Mg-24 and the spatial anisotropy of the p orbits of A. DOI: 10.1103/PhysRevC.87.021304
  • M. Kimura, Y. Taniguchi, Y. Kanada-En'Yo, H. Horiuchi, K. Ikeda
    Physical Review C - Nuclear Physics 87 (1) 1089-490X 2013/01/07 [Refereed][Not invited]
     
    We report the low-lying spectrum and collective β and γ deformation of 43S as investigated by antisymmetrized molecular dynamics. Our result successfully explains the observed data including an isomeric 7/21- state and illustrates the coexistence of the prolate-deformed ground band with a vanishing N=28 shell gap, a triaxially deformed isomeric state, and an oblate-deformed excited band at very low excitation energies. © 2013 American Physical Society.
  • Takenori Sumi, Kosho Minomo, Shingo Tagami, Masaaki Kimura, Takuma Matsumoto, Kazuyuki Ogata, Yoshifumi R. Shimizu, Masanobu Yahiro
    Physical Review C - Nuclear Physics 85 (6) 1089-490X 2012/06/19 [Refereed][Not invited]
     
    Deformations of Ne isotopes in the island of inversion are determined by the folding model description of the interaction cross sections measured for 28-32Ne isotopes incident on a 12C target at 240 MeV/nucleon, using the Melbourne g-matrix interaction and the nuclear densities calculated by antisymmetrized molecular dynamics (AMD). The double folding model with the AMD density well reproduces the measured interaction cross sections, if the tail correction is made to the AMD density for 31Ne. The quadrupole deformation determined is around 0.4 in the island of inversion and 31Ne is a halo nucleus with large deformation. We propose the Woods-Saxon model with the AMD deformation and a suitably chosen parametrization set as an approximate but simple method to reproduce the AMD density with the tail correction. The angular momentum projection is essential to obtain the large deformation in the island of inversion. Effects of the pairing correlation are investigated. © 2012 American Physical Society.
  • Takenori Sumi, Kosho Minomo, Shingo Tagami, Masaaki Kimura, Takuma Matsumoto, Kazuyuki Ogata, Yoshifumi R. Shimizu, Masanobu Yahiro
    PHYSICAL REVIEW C 85 (6) 2469-9985 2012/06 [Refereed][Not invited]
     
    Deformations of Ne isotopes in the island of inversion are determined by the folding model description of the interaction cross sections measured for Ne28-32 isotopes incident on a C-12 target at 240 MeV/nucleon, using the Melbourne g-matrix interaction and the nuclear densities calculated by antisymmetrized molecular dynamics (AMD). The double folding model with the AMD density well reproduces the measured interaction cross sections, if the tail correction is made to the AMD density for Ne-31. The quadrupole deformation determined is around 0.4 in the island of inversion and Ne-31 is a halo nucleus with large deformation. We propose the Woods-Saxon model with the AMD deformation and a suitably chosen parametrization set as an approximate but simple method to reproduce the AMD density with the tail correction. The angular momentum projection is essential to obtain the large deformation in the island of inversion. Effects of the pairing correlation are investigated.
  • Masahiro Isaka, Hiroaki Homma, Masaaki Kimura, Akinobu Dote, Akira Ohnishi
    PHYSICAL REVIEW C 85 (3) 0556-2813 2012/03 [Refereed][Not invited]
     
    The positive-parity states of Mg-25(Lambda) with a Lambda hyperon in s orbit were studied with the antisymmetrized molecular dynamics for hypernuclei. We discuss two bands of Mg-25(Lambda) corresponding to the K-pi = 0(+) and 2(+) bands of Mg-24. It is found that the energy of the K-pi = 2(+) circle times Lambda(s) band is shifted up by about 200 keV compared to Mg-24. This is because the Lambda hyperon in s orbit reduces the quadrupole deformation of the K-pi = 0(+) circle times Lambda(s) band, while it does not change the deformation of the K-pi = 2(+) circle times Lambda(s) band significantly.
  • Masaaki Kimura, Ryosuke Yoshida, Masahiro Isaka
    PROGRESS OF THEORETICAL PHYSICS 127 (2) 287 - 301 0033-068X 2012/02 [Refereed][Not invited]
     
    By using the antisymmetrized molecular dynamics with Cogny effective interaction, the low-lying spectrum and the E2 transition rates of Mg-24 are studied. On the basis of the comparison of the spectrum with observations, the importance of gamma deformation in both positive- and negative-parity states is emphasized. Among the seven bands obtained, K-pi = 2(+), 0(-) and 3(-) bands are triaxial deformed, and the inclusion of the degree of freedom of gamma deformation is found to be essential to describe them.
  • Yoshiko Kanada-En'yo, Masaaki Kimura, Akira Ono
    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS (1) 2050-3911 2012 [Refereed][Not invited]
     
    Structure and reaction studies using the antisymmetrized molecular dynamics (AMD) method are reviewed. Applications of time-independent and time-dependent versions of AMD are described. In applications of time-independent AMD to nuclear structure studies, the structures of neutron-rich nuclei such as Be, C, Ne, and Mg isotopes are described, focusing on cluster aspects. The important roles of valence neutrons are discussed. The results suggest that a variety of cluster structures appear in unstable nuclei as well as in stable nuclei. Deformation and cluster phenomena in Z similar to N nuclei in p-and sd-shell regions are also discussed. The applications of time-dependent AMD include various topics such as fragmentation in heavy-ion collisions as well as nuclear responses. The AMD calculations successfully describe multifragmentation, which is one of the remarkable phenomena observed in heavy-ion collisions. The approach is able to link reactions and nuclear matter properties. The studies suggest the important balance between single-particle motions and correlations to form clusters and fragments.
  • Kosho Minomo, Takenori Sumi, Masaaki Kimura, Kazuyuki Ogata, Yoshifumi R. Shimizu, Masanobu Yahiro
    PHYSICAL REVIEW LETTERS 108 (5) 052503  0031-9007 2012/01 [Refereed][Not invited]
     
    We perform the first quantitative analysis of the reaction cross sections of Ne28-32 by C-12 at 240 MeV/nucleon, using the double-folding model with the Melbourne g matrix and the deformed projectile density calculated by antisymmetrized molecular dynamics. To describe the tail of the last neutron of Ne-31, we adopt the resonating group method combined with antisymmetrized molecular dynamics. The theoretical prediction excellently reproduces the measured cross sections of Ne28-32 with no adjustable parameters. The ground state properties of Ne-31, i.e., strong deformation and a halo structure with spin parity 3/2(-), are clarified.
  • Kosho Minomo, Takenori Sumi, Masaaki Kimura, Kazuyuki Ogata, Yoshifumi R. Shimizu, Masanobu Yahiro
    PHYSICAL REVIEW C 84 (3) 0556-2813 2011/09 [Refereed][Not invited]
     
    The isotope dependence of measured reaction cross sections in the scattering of (28) (32)Ne isotopes from a (12)C target at 240 MeV/nucleon is analyzed by the double-folding model with the Melbourne g matrix. The density of the projectile is calculated by the mean-field model with the deformed Woods-Saxon potential. The deformation is evaluated by antisymmetrized molecular dynamics. The deformation of the projectile enhances calculated reaction cross sections to the measured values.
  • Masahiro Isaka, Masaaki Kimura, Akinobu Dote, Akira Ohnishi
    PHYSICAL REVIEW C 83 (5) 0556-2813 2011/05 [Refereed][Not invited]
     
    The low-lying states of Ne-21(Lambda) are studied with antisymmetrized molecular dynamics for hypernuclei. We have obtained ten rotational bands where the number of bands are increased compared to Ne-20 by adding a Lambda hyperon. Among them, we focus on the K-pi = 0(1)(+) circle times Lambda(s) and K-pi = 0(1)(-) circle times Lambda(s) bands. The former has a shell-model-like structure that has Lambda in an s wave coupled to the ground band of Ne-20. The latter is a cluster state that has a alpha + O-17(Lambda) dicluster structure. The difference between their structures leads to the binding energy of Lambda particle B-Lambda and reduction of the E2 transition probabilities B(E2).
  • M. Kimura, N. Furutachi
    PHYSICAL REVIEW C 83 (4) 0556-2813 2011/04 [Refereed][Not invited]
     
    The alpha-cluster structure of F isotopes has been studied based on antisymmetrized molecular dynamics. By using the constraint on the principal quantum number, various neutron configurations are investigated. It is found that a proton excitation into an sd shell does not necessarily induce alpha clustering in (21)F and (23)F. However, once one or two neutrons are excited into the pf shell together with a proton excitation, the core nuclei have alpha clustering. The calculation is extended toward the neutron drip line. The neutron-rich F isotopes also have alpha clustering in the excited states and their excitation energy greatly decreases toward the neutron drip line. The relation between the reduction of their excitation energies and the breaking of the neutron magic number N = 20 is suggested.
  • M. Isaka, M. Kimura, A. Dote, A. Ohnishi
    PHYSICAL REVIEW C 83 (4) 0556-2813 2011/04 [Not refereed][Not invited]
     
    An extended version of antisymmetrized molecular dynamics was developed to study the structure of p-sd shell hypernuclei. By using an effective Lambda N interaction, we investigated the energy curves of (9)(Lambda)Be, (13)(Lambda)C, and (20,21)(Lambda)Ne as a function of nuclear quadrupole deformation. The changes to nuclear deformation caused by Lambda particles are discussed. We found that Lambda in the p wave enhances nuclear deformation, while that in the s wave reduces it. This effect is most prominent in (13)(Lambda)C. The possibility of parity inversion in (20)(Lambda)Ne is also examined.
  • H. Matsumiya, K. Tsubakihara, M. Kimura, A. Dote, A. Ohnishi
    PHYSICAL REVIEW C 83 (2) 0556-2813 2011/02 [Refereed][Not invited]
     
    A theoretical framework of coupled-channels antisymmetrized molecular dynamics that describes the multistrangeness system with mixing between different baryon species is developed and applied to C-12(Lambda) and Be-12(Xi). By introducing a minor modification to the YN G-matrix interaction derived from the Nijmegen model-D, the low-lying level structure and production cross section of C-12(Lambda) are reasonably described. It is found that the low-lying states of Be-12(Xi) are dominated by the B-11 circle times Xi(-) channel and their order strongly depends on Xi N effective interactions used in the calculation. The calculated peak position of the production cross section depends on the Xi N effective interaction and the magnitude of spin-flip and non-spin-flip cross sections of K(-)p -> K+Xi(-) elemental processes. We suggest that the C-12(K-, K+)Be-12(Xi) reaction possibly provides us information about the Xi N interaction.
  • N. Furutachi, M. Kimura
    PHYSICAL REVIEW C 83 (2) 0556-2813 2011/02 [Refereed][Not invited]
     
    The stability of the three-alpha linear-chain structure of C-13 has been investigated with a microscopic 3 alpha + n model. We have found two excited rotational bands that have developed a three-alpha cluster structure in C-13. The lower band built on 3/2(2)(-) state at 11.4 MeV has the bent three-alpha linear-chain structure, and this structure is stable against the bending motion of three-alpha clusters.
  • J. A. Maruhn, N. Loebl, A. S. Umar, Naoyuki Itagaki, M. Kimura, H. Horiuchi, A. Tohsaki
    MODERN PHYSICS LETTERS A 25 (21-23) 1866 - 1869 0217-7323 2010/07 [Refereed][Not invited]
     
    We present Skyrme-force Hartree-Fock calculations of metastable three-alpha chain-state configurations in C-12, C-16, and C-20. A microscopic dynamical study of reactions involving three He-4 clusters shows that the triple-alpha linear chain configuration of C-12 is formed with a certain lifetime and subsequently decays into a triangular configuration of C-12 and then to a configuration near the ground state.
  • Masaaki Kimura, Naoya Furutachi
    MODERN PHYSICS LETTERS A 25 (21-23) 1838 - 1841 0217-7323 2010/07 [Refereed][Not invited]
     
    The alpha-clustering and molecular-orbitals of (22)Ne and (22)Mg are investigated based on antisymmetrized molecular dynamics. The observed candidates for the alpha cluster states are understood as the molecular-orbital states and alpha+(18)O di-nuclei states. The molecular-orbitals in neutron-rich F isotopes are predicted and the drastic reduction of their excitation energy toward the neutron-drip line is discussed.
  • H. Matsumiya, K. Tsubakihara, M. Isaka, M. Kimura, A. Dote, A. Ohnishi
    NUCLEAR PHYSICS A 835 (1-4) 366 - 369 0375-9474 2010/04 [Refereed][Not invited]
     
    An extended version of the Antisymmetrized Molecular Dynamics (AMD) approach that describes the multi-strangeness system is suggested. A strong dependence of the (12)(Xi)Be ground-state doublet on the Xi N interaction was found, and a possibility of determining the Xi N interaction from the (12)C(K(+), K(-))(12)(Xi)Be reaction is suggested. A drastic structure change in (13)(Lambda)C is also discussed.
  • J. A. Maruhn, N. Loebl, N. Itagaki, M. Kimura
    NUCLEAR PHYSICS A 833 (1-4) 1 - 17 0375-9474 2010/02 [Refereed][Not invited]
     
    Using a Skyrme mean-field model, we investigate the linear-chain configurations of three alpha-clusters with four or eight additional valence neutrons in C-16 and C-20 and discuss the relation between the stability of such states and the neutron number. The Hartree-Fock solution is sought from an initial configuration with three alpha-clusters and the additional neutrons are prepared in wave functions of various symmetries. We find at least five different chain configurations in C-16 and one "closed shell" configuration in C-20 that appear as highly converged states in the Hartree-Fock iterations. We investigate their stability with respect to quadrupole and octupole distortions and find that they appear unstable with respect to bending deformations, but show lifetimes that may lead to observable resonance. (C) 2009 Published by Elsevier B.V.
  • Yasutaka Taniguchi, Yoshiko Kanada-En'Yo, Masaaki Kimura, Kiyomi Ikeda, Hisashi Horiuchi, Eiji Ideguchi
    Physical Review C - Nuclear Physics 82 0556-2813 2010/01/01 [Not refereed][Not invited]
     
    Superdeformed (SD) states in Ar40 have been studied using the deformed-basis antisymmetrized molecular dynamics. Low-energy states were calculated by the parity and angular momentum projection and the generator coordinate method (GCM). Basis wave functions were obtained by the energy variation with a constraint on the quadrupole deformation parameter β, while other quantities such as triaxiality γ were optimized by the energy variation. By the GCM calculation, an SD band was obtained just above the ground-state band. The SD band involves a Kπ=2+side band due to the triaxiality. The calculated electric quadrupole transition strengths of the SD band reproduce the experimental values appropriately. Triaxiality is significant for understanding low-lying states. © 2010 The American Physical Society.
  • Yasutaka Taniguchi, Yoshiko Kanada-En'yo, Masaaki Kimura
    PHYSICAL REVIEW C 80 (5) 0556-2813 2009/11 [Refereed][Not invited]
  • Yasutaka Taniguchi, Yoshiko Kanada En'yo, Masaaki Kimura
    PHYSICAL REVIEW C 80 (4) 0556-2813 2009/10 [Refereed][Not invited]
     
    We have studied positive-parity states of Si-28 using antisymmetrized molecular dynamics and multiconfiguration mixing with constrained variation. Applying constraints to the cluster distance and the quadrupole deformation of the variational calculation, we have obtained basis wave functions that have various structures such as alpha-Mg-24 and C-12-O-16 cluster structures as well as deformed structures. Superposing those basis wave functions, we have obtained a oblate ground-state band, a beta vibration band, a normal-deformed prolate band, and a superdeformed band. It is found that the normal-deformed and superdeformed bands contain large amounts of the C-12-O-16 and alpha-Mg-24 cluster components, respectively. The results also suggest the presence of two excited bands with the developed alpha-Mg-24 cluster structure, where the intercluster motion and the Mg-24-cluster deformation play important roles.
  • Naoya Furutachi, Masaaki Kimura, Akinobu Dote, Yoshiko Kanada-En'yo
    PROGRESS OF THEORETICAL PHYSICS 122 (4) 865 - 880 0033-068X 2009/10 [Refereed][Not invited]
     
    We propose here an extended framework for antisymmetrized molecular dynamics (AMD) to describe the halo structure involving core excitation. We have applied this model to He isotopes, (8)B, and (9)C. Binding energies and radii in He isotopes are reproduced well by the present model, and the wave functions describe the spatial extension of the density distribution. These results indicate that a reasonable description of the halo structure is achieved in this model. Furthermore, the halo structure involving core excitation is found in (8)B and (9)C. The cluster structure in the core plays an important role in explaining the observed electric quadrupole and magnetic dipole moments in these nuclei.
  • Yasutaka Taniguchi, Yoshiko Kanada-En'yo, Masaaki Kimura
    PROGRESS OF THEORETICAL PHYSICS 121 (3) 533 - 553 0033-068X 2009/03 [Refereed][Not invited]
     
    Structures of p- and sd-shell nuclei are studied with the deformed-basis antisymmetrized molecular dynamics method using the Gogny D1S and Skyrme SLy7 forces as effective interactions. By the energy variation with a constraint, energy curves as functions of quadrupole deformation parameter beta are obtained. The energy curves for sd-shell nuclei show structure change as a function of beta and suggest shape coexistence. Nuclear structures in the deformed region are discussed focusing on deformations and clustering. It is found that the deformations often involve cluster structures. Effective-interaction dependence is also discussed focusing on the comparison of the results obtained with the two effective interactions. Although the two forces give similar results when cluster structures do not develop clearly, they give different energies in the largely deformed region when an alpha cluster develops.
  • N. Itagaki, M. Kimura
    PHYSICAL REVIEW C 79 (3) 0556-2813 2009/03 [Refereed][Not invited]
     
    We systematically investigate the possibility that the s(2) configuration of the two neutrons in the middle of the nucleus is a characteristic bond of alpha-clusters in light neutron-rich nuclei. The series of cluster states seen in Be-10(2 alpha+2n) and C-14(3 alpha+2n) is extended to the cases of heavier nuclei, O-18(4 alpha+2n) and Ne-22(5 alpha+2n), and we show the appearance of cluster structure with the s(2) bond in the excited states by using a microscopic N alpha+2n model, in which the coupling with low-lying states is included.
  • Yoshiko Kanada-En'yo, Yusuke Kawanami, Yasutaka Taniguchi, Masaaki Kimura
    PROGRESS OF THEORETICAL PHYSICS 120 (5) 917 - 935 0033-068X 2008/11 [Refereed][Not invited]
     
    The excited states of B-13 were studied by a method of antisymmetrized molecular dynamics (AMD). In the excited states, we predicted many cluster states with large deformations that construct the rotational bands, K-pi = 3/2(-) and K-pi = 1/2(+), starting from 5 and 8 MeV, respectively. The neutron structure of the K-pi = 3/2(-) band is analogous to the Be-12 ground state with a 2 (h) over barw configuration. The K-pi = 3/2(-)-band members correspond to the experimental level at 10.22 MeV, which is suggested to be a high-spin state with the 2 (h) over barW configuration. In the predicted K-pi = 1/2(+) band, we found a very exotic molecular structure with a larger deformation than superdeformation. This largely deformed state is dominated by a 3 (h) over barw configuration with one proton and two neutrons in the sd shell. In highly excited states, well-developed Li-9 + alpha cluster structures were predicted.
  • Naoya Furutachi, Masaaki Kimura, Akinobu Dote, Yoshiko Kanada-En'yo, Shinsho Oryu
    PROGRESS OF THEORETICAL PHYSICS 119 (3) 403 - 420 0033-068X 2008/03 [Refereed][Not invited]
     
    Cluster structures of O-16,O-18 and O-20 are investigated using the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM). We have found the K-pi=0(2)(+) and 0(-) rotational bands of 180 that have prominent C-14+alpha cluster structure. The clustering systematics are richer in O-20. We suggest the presence of a K-pi=0(2)(+) band that is a mixture of the C+alpha+4n and C-14+He-6 cluster structures. K-pi=0(3)(+) and 0(-) bands that have prominent C-16+alpha cluster structure are also found.
  • N. Itagaki, Tz. Kokalova, M. Ito, M. Kimura, W. von Oertzen
    PHYSICAL REVIEW C 77 (3) 0556-2813 2008/03 [Refereed][Not invited]
     
    We have studied the alpha-condensed states of O-16 and Ne-20 based on a microscopic alpha-cluster model. This was performed by introducing a Monte Carlo technique for the description of the THSR (Tohsaki Horiuchi Schuck Ropke) wave function, which is called the "virtual THSR" wave function. Earlier microscopic calculations pointed out the possibility of the existence of four-alpha-cluster condensed states. Here, in addition to studying the four-alpha case, we also studied the case of five-alpha particles, for which the states are shown to be stable around the threshold energy even after taking into account the coupling effect between normal cluster states with O-16+alpha configurations.
  • Yasutaka Taniguchi, Masaaki Kimura, Yoshiko Kanada-En'yo, Hisashi Horiuchi
    PHYSICAL REVIEW C 76 (4) 0556-2813 2007/10 [Refereed][Not invited]
     
    We have studied the positive-parity states of (40)Ca using antisymmetrized molecular dynamics (AMD) and the generator coordinate method (GCM). Imposing two different kinds of constraints on the variational calculation, we have found various kinds of (40)Ca structures such as a deformed-shell structure, as well as alpha-(36)Ar and (12)C-(28)Si cluster structures. After the GCM calculation, we obtained a normal-deformed band and a superdeformed band together with their side bands associated with triaxial deformation. The calculated B(E2) values agreed well with empirical data. It was also found that the normal-deformed and superdeformed bands have non-negligible alpha-(36)Ar cluster and (12)C-(28)Si cluster components, respectively. This leads to the presence of an alpha-(36)Ar higher nodal band occurring above the normal-deformed band.
  • Y. Taniguchi, M. Kimura, Y. Kanada-En'yo, H. Horiuchi
    Nuclear Physics A 787 547 - 552 0375-9474 2007/05/01 [Not refereed][Not invited]
     
    We have studied the coexistence of cluster structure and mean-field-type structure in 40Ca using Antisymmetrized Molecular Dynamics (AMD) + Generator Coordinate Method (GCM). By energy variation with constraint, we calculated GCM basis wave functions. Superposing cluster structure wave functions and mean-field-type structure wave function, we found that α-36Ar and 12C-28Si cluster structure are important components of normal-deformed (ND) band of 40Ca and that of superdeformed (SD) band of 40Ca, respectively. © 2006 Elsevier B.V. All rights reserved.
  • M. Kimura
    Physical Review C - Nuclear Physics 75 (4) 0556-2813 2007/04/26 [Refereed][Not invited]
     
    The low-lying level structure of Mg31 has been investigated by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM) with the Gogny D1S force. It is shown that the N=20 magic number is broken and the ground state has a pure neutron 2p3h configuration. The coexistence of many-particle, many-hole states at very low excitation energy is discussed. © 2007 The American Physical Society.
  • Masaaki Kimura
    PHYSICAL REVIEW C 75 (3) 0556-2813 2007/03 [Refereed][Not invited]
     
    Focusing on alpha clustering, the structure of Ne-22 was studied. We predict the presence of the molecular orbital bands that have an alpha+ O-16 cluster core surrounded by two neutrons occupying the molecular orbitals, together with alpha+ O-18 molecular bands. The formation of the alpha+ O-16 cluster core and its close relation to the configuration of two valence neutrons are discussed.
  • N. Itagaki, M. Kimura, C. Kurokawa, M. Ito, W. von Oertzen
    PHYSICAL REVIEW C 75 (3) 0556-2813 2007/03 [Refereed][Not invited]
     
    We demonstrate based on a microscopic alpha-cluster model that alpha-condensed states appear not only in light nuclei such as C-12 and O-16 but also in heavier nuclei with a core at excitation energies corresponding to multi-alpha-threshold energies. To extend the study of normal alpha-condensed state to the cases of heavier nuclei with an inner strongly bound core (O-16) and also to non-4N-nuclei (e.g., 2 alpha+dineutron), we introduce a Monte Carlo technique for the description of the Schuck wave function, which are called "virtual Schuck" wave function.
  • J. A. Maruhn, Masaaki Kimura, S. Schramm, P. -G. Reinhard, H. Horiuchi
    PHYSICAL REVIEW C 74 (4) 0556-2813 2006/10 [Refereed][Not invited]
     
    In this article we examine to what extent traces of alpha clustering can be found in mean-field ground states of n alpha nuclei from Be-8 through Ar-36 as well as in some superdeformed states in S-32, Ar-36, and Ca-40. For this purpose we calculate the overlap of the mean-field Slater determinant with one containing pure Gaussians and perfect spin and isospin symmetry, optimizing the overlap by varying the alpha-particle positions and radii. In some cases a coherent sum over different configurations is also employed. We find quite large overlaps for some of the lighter systems that diminish for nuclei above Ne-20 but again strong clustering in Ar-36.
  • Masaaki Kimura
    MODERN PHYSICS LETTERS A 21 (31-33) 2461 - 2467 0217-7323 2006/10 [Refereed][Not invited]
     
    The low-lying level structure of Mg-31 has been investigated by the theoretical framework of deformed-basis antisymmetrized molecular dynamics (DAMD) plus generator coordinate method (GCM) with the Gogny D1S force. It is shown that the N=20 magic number is broken and the intruder configuration (neutron 2p3h configuration) dominates the ground state. The observed data such as the magnetic moment and beta decay strength are well reproduced.
  • M Kimura, H Horiuchi
    NUCLEAR PHYSICS A 767 58 - 80 0375-9474 2006/03 [Refereed][Not invited]
     
    The nucleus Ti-44 has low-lying levels of various kinds of mutually very different nuclear structure displaying the richness of the nuclear many-body dynamics. It is shown that the deformed-basis antisymmetrized molecular dynamics by the use of the Gogny D1S force reproduces successfully and unifiedly two types of coexistence phenomena in 44Ti. Namely, on one hand, the coexistence of the mean-field structure and the cluster structure is confirmed by verifying the normally deformed structure of the K-pi = 3(1)(-) band with a 1-particle-1-hole intrinsic configuration and the alpha + Ca-40 cluster structure of the K-pi = 0(2)(-) band. The mixed character of the mean-field-like structure and the alpha + Ca-40 cluster structure of the ground band is also shown. On the other hand, the coexistence of the normal deformed mean-field and the superdeformed mean-field is confirmed by verifying the triaxial superdeformation of the K-pi = 0(2)(+) band and the K-pi = 2(1)(+) band which has a 4-particle-4-hole intrinsic configuration. Good reproduction of the experimental data is shown for many kinds of quantities including the energy spectra, electric transition rates, alpha spectroscopic factors. Preliminary discussions are given on the existence of hyperdeformed excited states, the relation between superdeformation and clustering and so on. (c) 2005 Elsevier B.V. All rights reserved.
  • Y. Kanada-En'yo, M. Kimura
    Physical Review C - Nuclear Physics 72 (6) 0556-2813 2005/12 [Refereed][Not invited]
     
    Deformed states in Ca40 are investigated with a method of antisymmetrized molecular dynamics. Above the spherical ground state, rotational bands arise from a normal deformation and a superdeformation as well as an oblate deformation. The calculated energy spectra and E2 transition strengths in the superdeformed band reasonably agree to the experimental data of the superdeformed band starting from the 03+ state at 5.213 MeV. By the analysis of single-particle orbits, it is found that the superdeformed state has particle-hole nature of an 8p-8h configuration. One of new findings is parity asymmetric structure with C12+Si28-like clustering in the superdeformed band. We predict that C12+Si28 molecular bands may be built above the superdeformed band due to the excitation of intercluster motion. They are considered to be higher nodal states of the superdeformed state. We also suggest negative-parity bands caused by the parity asymmetric deformation. © 2005 The American Physical Society.
  • Y Kanada-En'yo, M Kimura
    PHYSICAL REVIEW C 72 (6) 2469-9985 2005/12 [Refereed][Not invited]
     
    Deformed states in Ca-40 are investigated with a method of antisymmetrized molecular dynamics. Above the spherical ground state, rotational bands arise from a normal deformation and a superdeformation as well as an oblate deformation. The calculated energy spectra and E2 transition strengths in the superdeformed band reasonably agree to the experimental data of the superdeformed band starting from the 0(3)(+) state at 5.213 MeV. By the analysis of single-particle orbits, it is found that the superdeformed state has particle-hole nature of an 8p-8h configuration. One of new findings is parity asymmetric structure with C-12+Si-28-like clustering in the superdeformed band. We predict that C-12+Si-28 molecular bands may be built above the superdeformed band due to the excitation of intercluster motion. They are considered to be higher nodal states of the superdeformed state. We also suggest negative-parity bands caused by the parity asymmetric deformation.
  • Y Kanada-En'yo, M Kimura
    PHYSICAL REVIEW C 72 (6) 2469-9985 2005/12 [Refereed][Not invited]
     
    To study isovector dipole responses of neutron-rich nuclei, we applied a time-dependent method of antisymmetrized molecular dynamics. The dipole resonances in Be, B, and C isotopes were investigated. In Be-10, B-15, and C-16, collective modes of the vibration between a core and valence neutrons cause soft resonances at the excitation energy E-x=10-15 MeV below the giant dipole resonance (GDR). In C-16, we found that a remarkable peak at E-x=14 MeV corresponds to the coherent motion of four valence neutrons against a C-12 core, whereas the GDR arises in the E-x > 20 MeV region because of vibration within the core. In B-17 and C-18, the dipole strengths in the low-energy region decline compared with those in B-15 and C-16. We also discuss the energy-weighted sum rule for the E1 transitions.
  • Y Kanada-En'yo, M Kimura, H Horiuchi
    EUROPEAN PHYSICAL JOURNAL A 25 305 - 310 1434-6001 2005 [Refereed][Not invited]
     
    Cluster structure in stable and unstable nuclei has been studied. We report recent developments of theoretical studies on cluster aspect, which is essential for structure study of light unstable nuclei. We discuss negative-parity bands in even-even Be and Ne isotopes and show the importance of cluster aspect. Three-body cluster structure and cluster crystallization are also introduced. It was found that the coexistence of cluster and mean-field aspect brings a variety of structures to unstable nuclei.
  • Yasutaka Taniguchi, Masaaki Kimura, Hisashi Horiuchi
    Progress of Theoretical Physics 112 (3) 475 - 487 0033-068X 2004/09 [Not refereed][Not invited]
     
    A new constraint of clustering for the AMD calculation is proposed. This constraint yields a significant improvement in the investigation of the cluster structure using AMD, which sometimes meets with difficulty in producing certain specific cluster configurations. The usefulness of this constraint is verified by applying it to the the study of the Kπ = 03 + band of 20Ne, which has been conjectured to have 2α-12C structure. This band is not easy to construct with AMD. We show that the constraint in the AMD+GCM calculation is effective for the purpose of obtaining the Kπ = 03+ band, which contains the 2α-12C structure as an important component.
  • Masaaki Kimura, Hisashi Horiuchi
    Nuclear Physics A 738 236 - 239 0375-9474 2004/06/28 [Not refereed][Not invited]
     
    The properties of the16O+16O molecular bands and their relation to the superdeformed band have been studied by the full microscopic theoretical framework of the deformed-base AMD. The obtained results show that the superdeformed state of the32S has a remarkable overlap with the16O+16O configuration. Moreover, when the system is excited, the excitation energy is devoted to excite the relative motion between twol6Os and the system has a more prominent16O+16O structure, though the band members are fragmented into several states. © 2004 Elsevier B.V. All rights reserved.
  • Y Kanada-En'yo, M Kimura, H Horiuchi
    NUCLEAR PHYSICS A 738 3 - 9 0375-9474 2004/06 [Refereed][Not invited]
     
    According to microscopic calculations with antisymmetrized molecular dynamics, we studied cluster features in stable and unstable nuclei. A variety of structure was found in stable and unstable nuclei in the p-shell and sd-shell regions. The structure of excited states of Be-12 was investigated, while in sd-shell nuclei we focused on molecular states and deformed states. The deformed states in Si-28 and Ca-40 were discussed in connection with the high-lying molecular states. Appealing molecular states in Ar-36 and Mg-24 were suggested. The results signified that both clustering of nucleons and mean-field formation are essential features in sd-shell nuclei as well as p-shell nuclei.
  • M Kimura, H Horiuchi
    PROGRESS OF THEORETICAL PHYSICS 111 (6) 841 - 855 0033-068X 2004/06 [Refereed][Not invited]
     
    The low-lying level structures of Ne-26, Ne-28 and Ne-30 which are related to the breaking of the N=20 shell closure have been studied in the framework of the deformed-basis antisymmetrized molecular dynamics plus generator coordinate method using the Gogny D1S force. The properties of the many-particle and many-hole states are studied as well as that of the ground band. We predict that the negative-parity states, in which neutrons are promoted into the pf-orbit from the sd orbit, have a small excitation energy in the cases of Ne-28 and Ne-30. We regard this to be a typical phenomena accompanying the breaking of the N=20 shell closure. It is also found that the neutron 4p4h structure of 30Ne appears at low excitation energy, which contains alpha+O-16 correlations.
  • M Kimura, H Horiuchi
    PHYSICAL REVIEW C 69 (5) 0556-2813 2004/05 [Refereed][Not invited]
     
    The relation between the superdeformed band of S-32 and O-16+ O-16 molecular bands is studied by the deformed-basis antisymmetrized molecular dynamics with the Gogny D1S force. It is found that the obtained superdeformed band members of S have a considerable amount of the O-16+ O-16 component. Above the superdeformed band, we have obtained two excited rotational bands which have more prominent character of the O-16+ O-16 molecular band. These three rotational bands are regarded as a series of O-16+ O-16 molecular bands which were predicted by using the unique O-16- O-16 optical potential. As the excitation energy and principal quantum number of the relative motion increase, the O-16+ O-16 cluster structure becomes more prominent but at the same time, the band members are fragmented into several states.
  • Y Kanada-En'yo, M Kimura, H Horiuchi
    NUCLEAR PHYSICS A 734 341 - 344 0375-9474 2004/04 [Refereed][Not invited]
  • M Kimura
    PHYSICAL REVIEW C 69 (4) 0556-2813 2004/04 [Refereed][Not invited]
     
    A new theoretical framework is presented that uses a localized triaxially deformed Gaussian as the single-particle wave packet. The model space enables us to adequately describe both the deformed mean-field structure and the cluster structure within the same framework. The improvement over the original version of antisymmetrized molecular dynamics which uses the spherical Gaussian is verified by its application to the Ne-20 nucleus. The coexistence and interplay of the cluster structure and the deformed mean-field structure in the low-excited states of Ne-20 is studied. In particular, the intraband E2 transition probabilities in K-pi=0(1)(+) and 2(-) bands are reproduced without any effective charge.
  • M Kimura, H Horiuchi
    NUCLEAR PHYSICS A 722 507C - 511C 0375-9474 2003/07 [Refereed][Not invited]
  • Y Kanada-En'yo, M Kimura, H Horiuchi
    COMPTES RENDUS PHYSIQUE 4 (4-5) 497 - 520 1631-0705 2003/05 [Refereed][Not invited]
     
    The AMD theory for nuclear structure is explained by showing its actual applications. First the formulation of AMD including various refined versions is briefly presented and its characteristics are discussed, putting a stress on its nature as an ab initio theory. Then we demonstrate fruitful applications to various structure problems in stable nuclei, in order to explicitly verify the ab initio nature of AMD, especially the ability to describe both mean-field-type structure and cluster structure. Finally, we show the results of applications of AMD to unstable nuclei, from which we see that AMD is powerful in elucidating and understanding various types of nuclear structure of unstable nuclei. (C) 2003 Academie des sciences. Published by Editions scientifiques et medicales Elsevier SAS. All rights reserved.
  • Masaaki Kimura, Hisashi Horiuchi
    Progress of Theoretical Physics 483 - 487 0033-068X 2002/12/01 [Not refereed][Not invited]
     
    The neutron-rich nuclei 32Mg and 30Ne are studied using a new version of antisymmetrized molecular dynamics (AMD). After the angular-momentum projection, 32Mg and 30Ne have largely deformed ground states, and the experimental data for 32Mg are reproduced with reasonable accuracy. The ground states of these nuclei have neutron 2p2h structure. We also have studied the negative-parity states of these nuclei. Their lowest negative-parity states which have spin-parity 1- have quite small excitation energies compared to stable N = 20 isotones. By using the Gogny force, their excitation energies have calculated to be 2.4 MeV for 30Ne and 2.3 MeV for 32Mg and these 1- states have neutron 3p3h structure.
  • M Kimura, H Horiuchi
    PROGRESS OF THEORETICAL PHYSICS 107 (1) 33 - 42 0033-068X 2002/01 [Refereed][Not invited]
     
    The neutron-rich nuclei Mg-32 and Ne-30 are studied using a new version of antisymmetrized molecular dynamics (AMD). Due to the use of a deformed Gaussian as the single particle wave packet, the description of the deformation properties of Mg isotopes is drastically improved, and l . s force is accounted for more largely and sufficiently. After the angular momentum projection, Mg-32 and Ne-30 have deformed ground states, and the experimental data for Mg-32 are reproduced with reasonable accuracy. The deformation of the mean field is found to be essential to describe these nuclei. The ground states of these nuclei have neutron 2p2h structure. In Ne-30, the cluster-like and the mean-field-like structures coexist. The ground state of 32Mg has a mean-field-like structure. In the vicinity of the ground state, this nucleus is expected to have excited status with cluster-like structure-that possesses the neutron 4p4h configuration.
  • M Kimura, Y Sugawa, H Horiuchi
    PROGRESS OF THEORETICAL PHYSICS 106 (6) 1153 - 1177 0033-068X 2001/12 [Refereed][Not invited]
     
    Employing the Gogny force as an effective force. we study the ground state properties of light nuclei using antisymmetrized molecular dynamics (AMD). In a previous paper, we discussed the nuclear binding energies and nuclear radii of He. Be, C, O, Ne and Mg isotopes. In this paper, we mainly consider the deformation properties and the clustering nature of these isotopes. By comparing the calculated results with the AMD results by use of the Skyrme-III (SIII) force, we investigated the differences and similarities between the SIII force and the Gogny force. We find that the Gogny force yields rather better binding energy and larger deformation than the SKI force. We carry out he parity-projected calculations. Parity projection enhances the parity-violating deformation and the cluster structure of certain nuclei. Shape of the deformation energy surface is also changed by parity projection. This causes a competition between the mean-field-like structure and the cluster-like structure. A modified version of AMID, which employs deformed Gaussian wave packets instead of spherical ones, is shown to give large quadrupole moments in the case of Mg isotopes.
  • Y Sugawa, M Kimura, H Horiuchi
    PROGRESS OF THEORETICAL PHYSICS 106 (6) 1129 - 1152 0033-068X 2001/12 [Refereed][Not invited]
     
    Employing the Gogny force as an effective force. we study the ground state properties of light nuclei using antisymmetrized molecular dynamics (AMD). In this study, we are mainly concerned with the binding energies and radii of light even-Z isotopes, namely He. Be, C. O, Ne and Mg. Using a new technique to calculate the density dependent term of the effective force, we have realized fast and accurate calculations. from a comparison with Skyrme SIII results within the same AMD framework, we find that the Gogny and SIII forces well reproduce the experimental binding energies of stable nuclei. The two forces give almost equal radii, except in the case of Be-7 and Be-9. For both forces, approximate treatment of the center-of-mass kinetic energy causes overestimation of the binding energy compared with the exact treatment. It also causes a decrease of the nuclear deformation compared with the exact treatment. We also carry out an energy variation after the parity projection. With regard to the binding energies and radii, parity-projected calculations do not exhibit a large difference compared to non-projected results, although the density distribution and clustering features are often significantly changed by the parity projection.

Books etc

  • Progress of time-dependent nuclear reaction theory
    Kimura Masaaki (Joint work)
    Bentham Science Publishers 2016
  • Clusters in Nuclei Vol. 1
    Kimura Masaaki (Joint work)
    Springer 2010

Conference Activities & Talks

  • 反対称化分子動力学による光核励起断面積の理論計算  [Invited]
    木村真明
    日本物理学会2020年秋季大会  2020/09
  • Time-dependent molecular dynamics approach to the photodisintegration of light nuclei  [Invited]
    Masaaki Kimura
    PANDORA Meeting  2020/07
  • Shape of light clustered nuclei  [Invited]
    Masaaki Kimura
    ECT* workshop, Light clusters in nuclei and nuclear matter,  2019/09
  • クラスター共鳴に対する新しい研究アプローチ  [Invited]
    木村真明
    基礎物理学研究所研究会「原子核でつむぐrプロセス」  2019/05
  • 核データセンターの活動と,宇宙核物理における役割  [Invited]
    木村真明
    核データと重元素合成を中心とする宇宙核物理研究会  2019/03
  • Shape of Carbon-12  [Invited]
    Masaaki Kimura
    Workshop on Nuclear Cluster Physics (WNCP2018)  2018/11
  • Structure and Responses of nuclei studied by realtime evolution method  [Invited]
    Kimura Masaaki
    6th International Conference on Collective Motion in Nuclei under Extreme Conditions  2018/10
  • Nuclear Clustering probed by Electron scattering  [Invited]
    Kimura Masaaki
    ECT* workshop,Probing exotic structre of short-lived nuclei by electron scattering  2018/07
  • Structure and decay patterns of pygmy dipole resonances  [Invited]
    Kimura Masaaki
    Nuclear Structure and Related Topics (NSRT2018)  2018/06
  • Nuclear Molecules in neutron-rich nuclei  [Invited]
    Kimura Masaaki
    State of the Art in Nuclear Cluster Physics (SOTANCP4)  2018/05
  • Structure and decay of PDR in Ne isotopes  [Invited]
    Kimura Masaaki
    Topical Workshop on Modern Aspects in Nuclear Structure  2018/02
  • Nuclear Clustering Probed by Nuclear Responses  [Invited]
    Kimura Masaaki
    Ito International Research Center (IIRC) Symposium “Perspectives of the Physics of Nuclear Structure  2017/11
  • Recent activities of Hokkaido University group  [Not invited]
    Kimura Masaaki
    Workshop on Nuclear Cluster Physics (WNCP2017)  2017/10
  • Nuclear Clustering Probed by the Isoscalar Responses  [Invited]
    Kimura Masaaki
    International Symposium on Physics of Unstable Nuclei  2017/09
  • Study of light nuclei based on the real time evoution method and antisymmetrized molecular dynamics  [Not invited]
    Kimura Masaaki
    72th JPS annual meetng  2017/03
  • Clustering and Nuclear responses  [Invited]
    Kimura Masaaki
    First Tsukuba-CCS-RIKEN joint workshop on microscopic theories of nuclear structure and dynamics  2016/12
  • Nuclear responses and Clustering phenomena  [Invited]
    Kimura Masaaki
    The International Workshop on Nuclear Cluster Physics (WNCP2016)  2016/11
  • Reaction cross sections and clustering in neutron-rich nuclei  [Not invited]
    Kimura Masaaki
    RCNP Symposium "current status and perspective of the study of proton and neutron distribution radii probed by total and charge-changing cross sections  2016/11
  • PDR in neutron-rich Ne isotopes  [Not invited]
    Kimura Masaaki
    2016 Autumn JPS meeting  2016/09
  • Clusters and Responses in Atomic nuclei  [Invited]
    Kimura Masaaki
    International workshop for the collective motions in nuclei  2016/07
  • Probing asymmetric cluster states using isoscalar monopole and dipole transitions  [Invited]
    Kimura Masaaki
    Mini-Workshop on Nuclear Clustering 2016  2016/07
  • Probing asymmetric cluster states of astrophysical interest using isoscalar monopole and dipole transitions  [Not invited]
    Kimura Masaaki
    14th International Symposium on Nuclei in the Cosmos XIV  2016/06
  • Probing asymmetric clusters by isoscalar monopole/dipole transitions  [Invited]
    Kimura Masaaki
    The 11th International Conference on Clustering Aspects of Nuclear Structure and Dynamics  2016/05
  • Nuclear clustering probed by monopole and dipole responses  [Invited]
    Kimura Masaaki
    Clustering effects of nucleons in nuclei and quarks in multi-quark states  2016/03
  • Structure and decay of 26Ne PDR  [Not invited]
    Kimura Masaaki
    71th JPS annual meetng  2016/03
  • Nuclear response functions and clustering aspects studied by Antisymmetrized Molecular Dynamics  [Not invited]
    Kimura Masaaki
    International Symposium on High Spectroscopy & Tensor Interactions (HST15)  2015/11
  • Electric dipole response of 26Ne and nature of pygmy resonance  [Not invited]
    Kimura Masaaki
    Computational Advances in Nuclear and Hadron Physics (CANHP 2015)  2015/10
  • monopole strength and clustering; a research plan  [Not invited]
    Kimura Masaaki
    International mini-workshop on alpha condensates and monopole excitations  2015/09
  • Triaxial deformation and Octupole mode of 44Ti superdeformed state  [Not invited]
    Kimura Masaaki
    Hokkaido workshop on many-nucleon correlations and clustering  2015/08
  • Exotic Nuclear Clustering near the Neutron Drip-Line Studied by Antisymmetrized Molecular Dynamics  [Invited]
    Kimura Masaaki
    Gordon Research Conference Nuclear Chemisty  2015/06
  • Superdeformed, Hyperdeformed states and clustering in A=40 mass region  [Not invited]
    Kimura Masaaki
    70th JPS annual meetng  2015/03
  • Clusters in N=Z nuclei proved by isoscalar monopole transitions  [Not invited]
    Kimura Masaaki
    International Symposium on Physics of Unstable Nuclei 2014  2014/11
  • Formation of clusters in stable and unstable nuclei explored by antisymmetrized molecular dynamics  [Invited]
    Kimura Masaaki
    Fourth Joint Meeting of the Nuclear Physics Divisions of APS and JPS  2014/10
  • Erosion of N=28 Shell Gap and Triple Shape Coexistence in the vicinity of 44S  [Not invited]
    Kimura Masaaki
    Fourth Joint Meeting of the Nuclear Physics Divisions of APS and JPS  2014/10
  • Erosion of N=28 Shell Gap and Triple Shape Coexistence in the vicinity of 44S  [Not invited]
    Kimura Masaaki
    The 2nd Conference on "Advances in Radioactive Isotope Science” (ARIS2014)  2014/06
  • Clustering aspects in N=Z nucleus 24Mg studied by antisymmetized molecular dynamics  [Invited]
    Kimura Masaaki
    3rd International Workshops on “State of the Art of Cluster Physics" (SOTANCP3)  2014/05
  • Island of Inversion studied by antisymmetrized molecular dynamics  [Invited]
    Kimura Masaaki
    The first RIBF Discussion Plus  2014/04
  • Coupling of deformed core and weakly bound neutron  [Not invited]
    Kimura Masaaki
    69th JPS annual meeting  2014/03
  • Triaxial deformation and shape coexistence in N=28 nuclei  [Not invited]
    Kimura Masaaki
    2013 Autumn JPS meeting  2013/09
  • Nuclear structure probed by Lambda particle  [Invited]
    Kimura Masaaki
    Cross over of Hadron and Nuclear Physics  2013/09
  • Shape coexistence and non-yrast states in neutron-rich N〜28 nuclei  [Not invited]
    Kimura Masaaki
    The 12th Asia Pacific Physics Conference (APPC12)  2013/07
  • Modifying and Probing Nuclear Structure using ? particle  [Invited]
    Kimura Masaaki
    Symposium:Quarks to Universe in Computational Science  2012/12
  • Shape Coexisting Phenomena in neutron-rich N=20 and 28 isotopes  [Invited]
    Kimura Masaaki
    Physics Opportunities using Compton Suppressed Ge Clover Array  2012/12
  • Collective motions and exotic deformations in neutron-rich nuclei  [Invited]
    Kimura Masaaki
    The Third International Symposium on Frontiers in Nuclear Physics  2012/11
  • Collective motions and exotic deformations in neutron-rich nuclei  [Invited]
    Kimura Masaaki
    The 8th China-Japan Joint Nuclear Physics Symposium  2012/10
  • Clustering aspects in highly excited states and neutro-rich nuclei  [Invited]
    Kimura Masaaki
    10th International Conference on Clustering Aspects of Nuclear Structure and Dynamics (CLUSTER12)  2012/09
  • Triaxial deformation and shape coexistence in the Island of Inversion  [Not invited]
    Kimura Masaaki
    2012 Autumn JPS meeting  2012/09
  • Shape coexistence in neutron-rich N=20 and 28 isotopes studied by anti-symmetrized molecular dynamics  [Invited]
    Kimura Masaaki
    Korean Physical Society Meeting  2011/10
  • Clustering aspects of highly excited and neutron-rich nuclei  [Invited]
    Kimura Masaaki
    YKIS2011, Frontier Issues in Physics of Exotic Nuclei  2011/10
  • Shape coexistence and shell evolution of N-28 system ? the case of 43S -  [Not invited]
    Kimura Masaaki
    2011 Autumn JSP meeting  2011/09
  • Monopole transition in 24Mg and Island of Inversion  [Invited]
    Kimura Masaaki
    Strategy meeting for the search of cluster gas states  2011/09
  • Clustering in 24Mg and monopole transitions studied by AMD  [Not invited]
    Kimura Masaaki
    66th JPS annual meeting  2011/03
  • Landscape of the island of inversion studied by AMD  [Invited]
    Kimura Masaaki
    Many body correlations from dilute to dense nuclear matter  2011/02
  • Systematic study of many-particle and many-hole states in and around the island of inversion  [Invited]
    Kimura Masaaki
    French Japanese Symposium on Nuclear Structure Problems  2011/01
  • Systematic study of the Island of Inversion by AMD  [Not invited]
    Kimura Masaaki
    University of Aizu-JUSTIPEN-EFES Symposium on "Cutting-Edge Physics of Unstable Nuclei"  2010/11
  • Clustering aspects in excited and neutron-rich nuclei  [Invited]
    Kimura Masaaki
    Clustering and nucleon correlations  2010/09
  • Structure of N=21 isotones  [Not invited]
    Kimura Masaaki
    2010 Autumn JPS meeting  2010/09
  • Spectroscopy of N=21 isotones in the Island of Inversion with AMD  [Not invited]
    Kimura Masaaki
    EMMI-EFES workshop on neutron-rich exotic nuclei  2010/06
  • Systematic study of mpmh states in the Island of Inversion  [Not invited]
    Kimura Masaaki
    State of the Art in Nuclear Cluster Physics, SOTANCP2  2010/05
  • Molecular States and Molecular Orbitals in N≠Z sd-shell nuclei  [Not invited]
    Kimura Masaaki
    Frontiers of Researches in Exotic Nuclear Structures  2010/05
  • Molecular states in 21Na and 21Ne studied by AMD  [Not invited]
    Kimura Masaaki
    65th JPS annual meeting  2010/03
  • Shape coexistence and Triaxial deformation in Cr isotopes studied by AMD-HFB model  [Invited]
    Kimura Masaaki
    EFES-LIA workshop on the Nuclear Energy Density Functional Method  2010/02
  • “Molecular states in neutron-rich sd-pf shell nuclei  [Not invited]
    Kimura Masaaki
    Direct Reactions with Exotic Beams, DREB2009  2009/12
  • Molecular states and the island of inversion  [Invited]
    Kimura Masaaki
    The 7th Japan-China Joint Nuclear Physics Symposium  2009/11
  • Spin-dependence of ?N interaction and ? hypernuclear production spectrum  [Not invited]
    Kimura Masaaki
    10th International Conference on Hypernuclear and Strange Particle Physics  2009/09
  • Molecular orbitals in neutron-rich nuclei  [Not invited]
    Kimura Masaaki
    10th International Conference on Nucleus-Nucleus Collisions  2009/08
  • Shape coexistence and Triaxial deformation of Cr isotopes  [Not invited]
    Kimura Masaaki
    Development of nuclear structure models from the view point of nuclear force  2009/05
  • Molecular states of neutron-rich sd-pf shell nuclei studied by AMD  [Not invited]
    Kimura Masaaki
    KGU Yokohama Autumn School of Nuclear Physics  2008/10
  • Clustering aspects in neutron-rich sd-pf shell nuclei  [Not invited]
    Kimura Masaaki
    JUSTIPEN-EFES-Hokudai-UNEDF meeting  2008/07
  • The spectroscopy of the island of inversion and molecular orbitals  [Not invited]
    Kimura Masaaki
    The 9th international conference on Clustering Aspects of Nuclear Structure and Dynamics  2007/09
  • Molecular orbitals in the island of inversion  [Not invited]
    Kimura Masaaki
    The International Symposium on Physics of Unstable Nuclei (ISPUN08)  2007/07
  • Clustering Aspects of sd-shell nuclei studied by AMD  [Invited]
    Kimura Masaaki
    International Symposium on Structure of Exotic Nuclei and Nuclear Forces  2006/03
  • Molecular-Orbital and Di-Nuclei States in F and Ne isotopes  [Not invited]
    Kimura Masaaki
    YITP Workshop on Binding Mechanism and New Dynamics in Weakly Bound System  2005/12
  • 16O+16O molecular bands and their relation to the superdeformed band of 32S  [Not invited]
    Kimura Masaaki
    The 8th international conference on Clustering Aspects of Nuclear Structure and Dynamics  2003/11
  • Introduction of the deformed-basis AMD and application to the stable and unstable nuclei  [Not invited]
    Kimura Masaaki
    International Symposium on Physics of Unstable Nuclei  2002/11
  • Many particle and many hole states of sd-pf shell stable and unstable nuclei  [Not invited]
    Kimura Masaaki
    Study weekend of drip-line nuclei  2002/06
  • Breaking of magic number N=20 studied by the new version of AMD  [Not invited]
    Kimura Masaaki
    10th Yukawa International Seminar Physics of Unstable Nuclei  2001/11

MISC

  • M. Kimura  Journal of Physics: Conference Series  321-  (1)  2011  [Refereed][Not invited]
     
    Deformation and many particle and many hole configurations in the island of inversion are investigated with Antisymmetrized Molecular Dynamics (AMD). The result suggests the coexistence of many particle and many hole configurations with different deformation at small excitation energy. In the case of 33Mg, we suggest the negative-parity assignment for the ground state. Other particle hole configurations are predicted as the excited states. © Published under licence by IOP Publishing Ltd.
  • Y. Kanada-En'yo, M. Kimura, F. Kobayashi, T. Suhara, Y. Taniguchi  INTERNATIONAL SYMPOSIUM ON NEW FACES OF ATOMIC NUCLEI: FESTSCHRIFT IN HONOUR OF AKITO ARIMA'S 80TH BIRTHDAY  1355-  2011  [Refereed][Not invited]
     
    We report some topics on cluster structures studied by using a theoretical method of antisymmetrized molecular dynamics(AMD). Cluster features of p-shell and sd-shell nuclei are discussed. In particular, three alpha cluster structures in the excited states of C-12 and C-14 are focused. Dineutron correlations in neutron-rich nuclei are also discussed.
  • Y. Kanada-En'Yo, M. Kimura  Lecture Notes in Physics  818-  129  -164  2010  [Refereed][Not invited]
  • M. Kimura, N. Furutachi, Y. Kanada-En'yo  Nuclear Physics A  834-  (1-4)  482c-484c  2010  [Refereed][Not invited]
  • Kiyoshi Kato, Masaaki Kimura, Naoya Furutachi, Tomoaki Togashi, Ayano Makinaga, Naohiko Otuka  TOURS SYMPOSIUM ON NUCLEAR PHYSICS AND ASTROPHYSICS - VII  1238-  199  -+  2010  [Refereed][Not invited]
     
    The activities of the Japan Nuclear Reaction Data Centre is explained. The main task of the centre is data compilation of Japanese nuclear reaction data in collaboration of the International Network of Nuclear Reaction Data Centres. As one of recent activities, preparation of a new database (NRDF/A) and evaluation of astronuclear reaction data are reported. Collaboration in the nuclear data activities among Asian countries is proposed.
  • Yasutaka Taniguchi, Yoshiko Kanada-En'yo, Masaaki Kimura  INTERNATIONAL JOURNAL OF MODERN PHYSICS A  24-  (11)  2069  -2075  2009/04  [Refereed][Not invited]
     
    Positive-parity states of Si-28 are studied with antisymmetrized molecular dynamics and multi-configuration mixing focusing on clustering and deformations. By superposition of wave functions obtained by energy variation imposing constraints on quadrupole deformation parameter beta and distance between a and Mg-24, and C-12 and O-16 clusters, two oblate bands, two prolate bands and developed alpha-Mg-24 band are obtained. It is found that cluster structure components are contained in those bands.
  • Naoyuki Itagaki, Masaaki Kimura, Makoto Ito, Shigeyoshi Aoyama, Yuichi Hirata  INTERNATIONAL JOURNAL OF MODERN PHYSICS A  24-  (11)  2019  -2026  2009/04  [Refereed][Not invited]
     
    The condensed states of alpha-clusters or di-neutrons are studied by introducing a Monte Carlo technique for the description of the THSR (Tohsaki Horiuchi Schuck Ropke) wave function. The condensed state of five alpha particles is shown to be stable around the threshold energy even after taking into account the coupling effect between normal cluster states with O-16+alpha configurations. Next, the mixing of di-neutron components in He-8 is studied. The ground state of 8He corresponds to the sub-closed-shell configuration of the spin-orbit favored orbits (p(3/2)) for the neutrons, and the shell-model-like configuration is considered to be dominant. However, He-8 is a drip-line nucleus with a two-neutron separation energy of 2.1 MeV, and the di-neutron configuration, which is a characteristic feature of the weakly bound systems, mixes in the ground state. Finally, characteristic mechanism for the binding of clusters in neutron-rich nuclei (s(2) bond) is discussed.
  • N. Furutachi, M. Kimura  19TH INTERNATIONAL IUPAP CONFERENCE ON FEW-BODY PROBLEMS IN PHYSICS  3-  2009  [Refereed][Not invited]
     
    We have studied the structures of He isotopes, B-8, and C-9 by using an extended framework of antisymmetrized molecular dynamics, which is designed to describe the halo structure and the core excitation simultaneously. The effectiveness of the present framework in describing the halo structure is demonstrated in the calculated results of He isotopes. The structures of B-8 and C-9 are discussed focusing on the halo structure and the core excitation in these nuclei. We have found the cluster structures in the cores of these nuclei, which plays an important role in explaining the observed physical quantities.
  • Yasutaka Taniguchi, Yoshiko Kanada-En'yo, Masaaki Kimura  19TH INTERNATIONAL IUPAP CONFERENCE ON FEW-BODY PROBLEMS IN PHYSICS  3-  2009  [Refereed][Not invited]
     
    We have studied positive-parity states of Si-28 using antisymmetrized molecular dynamics and multi-configuration mixing with constrained variation. Applying constraints to the cluster distance and the quadrupole deformation of the variational calculation, we have obtained basis wave functions that have various structures such as alpha-Mg-24 and C-12-O-16 cluster structures as well as deformed structures. Superposing those basis wave functions, we have obtained a oblate ground state band, a beta vibration band, a normal-deformed prolate band, and a superdeformed band. It is found that the superdeformed bands contain large amounts of the alpha-Mg-24 cluster components. The results also suggest the presence of two excited bands with the developed alpha-Mg-24 cluster structure, where the inter-cluster motion and the Mg-24-cluster deformation play important roles.
  • Yoshiko Kanada-En'yo, Masaaki Kimura, Yasutaka Taniguchi, Tadahiro Suhara  INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS  17-  (10)  2336  -2344  2008/11  [Refereed][Not invited]
     
    We report three-center cluster structures in the excited states of (11)B((11)C), (8)He and (14)C based on theoretical calculations with the antisymmetrized molecular dynamics (AMD). In particular we discuss the cluster gas-like states 2 alpha + t(2 alpha + (3)He) in (11)B((11)C) and alpha + 2n + 2n in (8)He. In (14)C, the 3 alpha linear-chain structure is discussed.
  • Y. Kanada-En'yo, Y. Taniguchi, M. Kimura  NUCLEAR PHYSICS A  805-  392C  -399C  2008/06  [Refereed][Not invited]
     
    We investigated molecular states and cluster gas-like states in light nuclei based on theoretical calculations with antisymmetrized molecular dynamics. The calculated results of (13)B suggest that largely deformed states construct rotational bands, K(pi) = 3/2(-) and K(pi) = 1/2(+), starting from 5 MeV and 8 MeV, respectively. The neutron structure of the K(pi) = 3/2(-) is analogous to the intruder ground state of (12)Be. In the predicted K(pi) = 1/2(+) band, we found largely deformed structure with a proton excited configuration. The band-head 1/(2)+ state is assigned to the 1/2(+)(4.83 MeV), which was experimentally suggested to be the proton intruder state. Structure of (8)He were also investigated. In the results, it was found that the ground state of (8)He has both the j-j coupling feature(p(3/2) closure) and the L-S coupling feature((4)He+2n+2n). The results also suggest possible existence of the 0(2)(+) state with dineutron gas-like structure of 4 (4)He+2n+2n, which has an analogy to the 3 alpha-cluster structure of the (12)C(0(2)(+)) state.
  • Yasutaka Taniguchi, Masaaki Kimura, Yoshiko Kanada-En'yo, Hisashi Horiuchi  PROTON EMITTING NUCLEI AND RELATED TOPICS  961-  261  -+  2007  [Refereed][Not invited]
     
    We have Studied the positive-parity states of Ca-40 using antisymmetrized molecular dynamics (AMD) and the generator coordinate method (GCM). Imposing two different kinds of constraints on the variational calculation, we have found various kinds of Ca-40 structures such as a deformed-shell structure, as well as alpha-Ar-36 and C-12-Si-28 cluster structures. After the GCM calculation, we obtained a normal-deformed band and a superdeformed band to-ether with their side bands associated with triaxial deformation. The calculated B(E2) values agreed well with empirical data. It was also found that the normal-deformed and superdeformed bands contain alpha-Ar-16 and C-12- Si-28 cluster structure components. respectively. This leads to the presence of an alpha-Ar-36 higher-nodal band occurring above the normal-deformed band.
  • Masaaki Kimura, Yasutaka Taniguchi, Yoshiko En'Yo, Hisashi Horiuchi  Journal of Physics: Conference Series  49-  200  -205  2006/10/10  [Not refereed][Not invited]
     
    The new clustering aspects of sd-shell nuclei found by the recent application of the antisymmetrized molecular dynamics are reported. In this paper we present two topics, "superdeformed band of 32S and 16O + 16O clustering" and "molecular-orbital and di-nuclei states in 22Ne". In the first topic, it will be shown that the superdeformed band of 32S has a considerable amount of 16O + 16O cluster component, and can be regarded as to belong to a family of the 16O + 16O molecular bands. In the second topic, the presence of the molecularorbital band which has an α + 16O cluster core surrounded by two covalently neutrons is suggested together with an α + 18O di-nuclei band. © 2006 IOP Publishing Ltd.
  • Yoshiko Kanada-En'yo, Masaaki Kimura  INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS  15-  (7)  1541  -1548  2006/10  [Refereed][Not invited]
     
    Structures of excited states in C-11 and B-11 were studied based on variational calculations after spin-parity projection in a framework of antisymmetrized molecular dynamics (AMD). The calculations systematically reproduce the experimental data of the transition strengths such as Gamov-Teller and Ml transitions. A well-developed cluster structure of 2 alpha+He-3(t) was found in the 3/2(3)(-) state of C-11(B-11), which can be assigned to the observed 3/2(3)(-) state at 8 MeV. The calculations reproduce the small B(GT;(11) B-g.s.->(11) C(3/2(3)(-))) measured in the recent experiments. It was suggested that the 3/2(3)(-) state has a dilute cluster state, and its features are similar to those of the 12C(0(2)(+)) which is considered to be a gas state of three a clusters. The structures of C-13 were also discussed.
  • Yasutaka Taniguchi, Masaaki Kimura, Hisashi Horiuchi  FRONTIERS IN NUCLEAR STRUCTURE ASTROPHYSICS, AND REACTIONS: FINUSTAR  831-  245  -+  2006  [Refereed][Not invited]
     
    We have studied the coexistence of cluster structure and mean-field-type structure in Ne-20 and Ca-40 using Antisymmetrized Molecular Dynamics (AMD) + Generator Coordinate Method (GCM). By energy variation with new constraint for clustering, we calculate cluster structure wave function. Superposing cluster structure wave functions and mean-field-type structure wave function, we found that Be-8-C-12, alpha-(36) At and C-12-Si-28 cluster structure are important components of K-pi = 0(3)(+) band of Ne-20, that of normal deformed band of Ca-40 and that of super deformed band of Ca-40, respectively.
  • H Horiuchi, Y Kanada-En'yo, M Kimura  NUCLEAR PHYSICS A  722-  80C  -84C  2003/07  [Refereed][Not invited]
  • H Horiuchi, Y Kanada-En'Yo, M Kimura  FRONTIERS OF COLLECTIVE MOTIONS (CM2002)  13  -19  2003  [Refereed][Not invited]
     
    Structure study by the use of AMD in stable and unstable nuclei is reviewed. We put some emphasis on the characteristic features of AMD approach which include variation after parity projection, variation after angular momentum projection, superposition of parity-spin projected AMD Slater determinants. Since AMD is an ab initio theory of nuclear structure, we can study cluster structure without assuming the existence of any clusters and can describe the coexistence of mean-field-type structure and cluster structure.@ Some examples of calculated results are shown by comparing with the experimental data. They are the studies on neutron-rich Li, BeCB isotopes, on the island of inversion around N=20, and on the excited bands with many-particle many-hole structure in Ti-44.
  • H Horiuchi, Y Kanada-En'yo, M Kimura  ACTA PHYSICA HUNGARICA NEW SERIES-HEAVY ION PHYSICS  18-  (2-4)  209  -213  2003  [Refereed][Not invited]
     
    Clustering in nuclei is discussed putting emphasis on the investigation of the role of nuclear clustering in neutron-rich nuclei. The subjects we discuss include clustering in neutron-rich Be, B and C isotopes, clustering in the island of inversion around N = 20, and clustering in the region with A approximate to 40. Be isotopes present us typical examples of clustering in neutron-rich nuclei not only in their ground band states but also in their excited band states, for which we show the analyses based on antisymmetrized molecular dynamics (AMD). Clustering in Be isotopes near neutron dripline is intimately related to the breaking of the neutron magic number N = 8. In this connection we report our study about the possible relation of the clustering with the breaking of the neutron magic number N = 20 in the island of inversion including Mg-32 and Ne-30. Our discussion is not only about the positive parity states but also about negative parity states. Recently in the latter half of sd shell and in the pf shell many excited rotational bands with large deformation have been found to exist. Since the first excited K-pi = 0(+) and K-pi = 0(-) bands in Ca-40 have been regarded as constituting inversion doublet bands having the Ar-36 + alpha structure, and since the first excited K-pi = 0(+) band in K-pi = 0(-) has been concluded to have Ca-40 + alpha structure through the a transfer reaction and by using the unique alpha optical potential on Ca-40, it is important to investigate the role of a clustering in these newly-found rotational bands with large deformation. We will report the AMD study about this problem.
  • M Kimura, H Horiuchi  PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT  (146)  483  -487  2002  [Refereed][Not invited]
     
    The neutron-rich nuclei Mg-32 and Ne-30 are studied using a new version of antisymmetrized molecular dynamics (AMD). After the angular-momentum projection, Mg-32 and Ne-30 have largely deformed ground states, and the experimental data for Mg-32 are reproduced with reasonable- accuracy. The ground states of these nuclei have neutron 2p2h structure. We also have studied the negative-parity states of these nuclei. Their lowest negative-parity states which have spin-parity 1(-) have quite small excitation energies compared to stable N = 20 isotones. By using the Gogny force, their excitation energies have calculated to be 2.4 MeV for Ne-30 and 2.3 MeV for Mg-32 and these 1(-) states have neutron 3p3h structure.
  • Y Kanada-En'yo, A Kimura, H Horiuchi  EXOTIC CLUSTERING  644-  188  -195  2002  [Refereed][Not invited]
     
    The structures of the ground and excited states of sd-shell nuclei: Ca-40 and Ar-36 were studied with a method of antisymmetrized molecular dynamics. Recently observed rotational bands were described with deformed intrinsic states which are dominated by excited configurations such as 4p - 4h, 8p - 8h and 4p - 8h states. The results showed the coexistence of various kinds of exotic shapes with oblate, prolate and large prolate deformatios in the low-energy region of Ca-40. Possible cluster aspects in heavy sd-shell nuclei were implied in these exotic shapes.
  • H Horiuchi, Y Kanada-En'yo, A Dote, M Kimura  FEW-BODY PROBLEMS IN PHYSICS '99  12-  125  -129  2000  [Refereed][Not invited]
     
    Formulation of AMD is briefly explained. It is explained that AMD can describe both mean field structure and cluster structure and also their coexistence. As an example to show this fact the results of the study of C-12 are reported. Then it is shown that AMD is useful for the study of unstable nuclei which show many unexpected features different from stable nuclei. Nobel features of unstable nuclei we discuss include molecular orbits in Be isotopes, novel type of clustering in B isotopes, and different deformation of proton and neutron distributions in C isotopes.

Research Grants & Projects

  • Novel approach for the Carbon burning processes based on alpha inelastic scattering
    Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2019/04 -2022/03 
    Author : 木村 真明
  • Nuclear structure and reaction simulation by supercomputing
    Hokkaido University:Information Initiative Center Budget for Collaboration research
    Date (from‐to) : 2020/04 -2021/03 
    Author : 升井洋志
  • Chaged particle reaction database
    Japan Society for the Promotion of Science:Grant-in-Aid for Publication of Scientific Research Results
    Date (from‐to) : 2020/04 -2021/03 
    Author : Kimura Masaaki
  • 大規模数値計算による原子核反応シミュレーションとデータベース構築
    Hokkaido University:Information Initiative Center Budget for Collaboration research
    Date (from‐to) : 2019/04 -2020/03 
    Author : 升井洋志
  • Chaged particle reaction database
    Japan Society for the Promotion of Science:Grant-in-Aid for Publication of Scientific Research Results
    Date (from‐to) : 2019/04 -2020/03 
    Author : Kimura Masaaki
  • Nuclear structure and reaction simulation by supercomputing
    Hokkaido University:Information Initiative Center Budget for Collaboration research
    Date (from‐to) : 2018/04 -2019/12 
    Author : Masui Hiroshi
  • Chaged particle reaction database
    Japan Society for the Promotion of Science:Grant-in-Aid for Publication of Scientific Research Results
    Date (from‐to) : 2018/04 -2019/03 
    Author : Kimura Masaaki
  • Study of cluster resonances probed by isoscalar monopole and dipole resonances, and its application to Carbon burning processes
    Japan Society for the Promotion of Science:Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2016/04 -2019/03 
    Author : Kimura Masaaki
  • Nuclear clustering and reactions studied by massive parallel computing
    Hokkaido University:Information Initiative Center Budget for Collaboration research
    Date (from‐to) : 2016/04 -2017/03 
    Author : Masui Hiroshi
  • Chaged particle reaction database
    Japan Society for the Promotion of Science:Grant-in-Aid for Publication of Scientific Research Results
    Date (from‐to) : 2013/04 -2017/03 
    Author : Kimura Masaaki
  • Theoretical study for neutron stars and neutron matter
    Japan Society for the Promotion of Science:Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
    Date (from‐to) : 2012/04 -2017/03 
    Author : Ohnishi Akira
  • Study of shape coexistence and novel type of neutron halo close to neutron drip line
    Japan Society for the Promotion of Science:Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2013/04 -2016/03 
    Author : Kimura Masaaki
  • Study of Mulecular states in Oxygen and Neon isotopes, and application to nucleosynthesis
    Japan Society for the Promotion of Science:Grant-in-Aid for Young Scientists (B)
    Date (from‐to) : 2010/04 -2013/03 
    Author : Kimura Masaaki
  • Study of molecular states in Oxygen and Neon isotopes and application to Nucleosynthesis
    Hokkaido University:President budget for young researcher
    Date (from‐to) : 2009/04 -2010/03 
    Author : Kimura Masaaki
  • Study of cluster correlation and molecules in sd-pf shell stable and unstable nuclei
    Japan Society for the Promotion of Science:Grant-in-Aid for JSPS Fellows
    Date (from‐to) : 2006/04 -2008/01 
    Author : Kimura Masaaki

Educational Activities

Teaching Experience

  • 宇宙理学特別講義1
    開講年度 : 2019
    課程区分 : 修士課程
    開講学部 : 理学院
  • 宇宙理学特別講義2
    開講年度 : 2019
    課程区分 : 修士課程
    開講学部 : 理学院

Campus Position History

  • 2016年4月1日 
    2018年3月31日 
    大学院理学研究院附属原子核反応データベース研究開発センター長
  • 2018年4月1日 
    2020年3月31日 
    大学院理学研究院附属原子核反応データベース研究開発センター長

Position History

  • 2016年4月1日 
    2018年3月31日 
    大学院理学研究院附属原子核反応データベース研究開発センター長
  • 2018年4月1日 
    2020年3月31日 
    大学院理学研究院附属原子核反応データベース研究開発センター長


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