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Hirokawa Jun

Faculty of Environmental Earth Science　Materials Science　Molecular Materials ChemistryAssociate Professor
Center for Environmental and Health SciencesAssociate Professor

Researcher basic information

■ Degree
  • 博士（理学）, 東京大学
■ URL
researchmap URLホームページURL■ Various IDs
Researcher number
  • 20262115
J-Global ID■ Research Keywords and Fields
Research Field
  • Nanotechnology/Materials, Fundamental physical chemistry
  • Nanotechnology/Materials, Green sustainable chemistry and environmental chemistry
  • Natural Science, Atmospheric and hydrospheric sciences
■ Educational Organization

Research activity information

■ Papers
■ Other Activities and Achievements
■ Books and other publications
■ Syllabus
  • ナノ環境材料化学特論Ⅰ, 2024年, 修士課程, 環境科学院
  • 環境科学総論, 2024年, 修士課程, 環境科学院
  • 化学Ⅰ, 2024年, 学士課程, 全学教育
■ Affiliated academic society
  • 日本分光学会
  • 日本化学会
  • 日本エアロゾル学会
  • 大気環境学会
  • 日本大気化学会
  • Japan Association of Aerosol Science and Technology
■ Research Themes
  • ウイルス粒子の個性に注目した細胞取り込み機構と応答スペクトルの解析
    科学研究費助成事業
    01 Apr. 2021 - 31 Mar. 2024
    藤岡 容一朗; 廣川 淳
    日本学術振興会, 基盤研究(B), 北海道大学, 21H02735
  • Impacts of Aerosols in East Asia on Plants and Human Health-Research Generalization
    Grants-in-Aid for Scientific Research
    13 Nov. 2008 - 31 Mar. 2014
    HATAKEYAMA Shiro; HONDA Yasushi; IZUTA Takeshi; TOHNO Susumu; SUGIMOTO Nobuo; HARA Hiroshi; OKUYAMA Kikuo; KAMIYA Hidehiro; HIROKAWA Jun; KANEYASU Naoki; FUNADA Ryo; MATSUDA Kazuhide; TAKANO Hirohisa; WANG Qingyue
    エアロゾルの化学、物理、工学などの研究者と植物生理の研究者、医学の研究者が連携してエアロゾルをキーワードに東アジアで増加するエアロゾルの発生、変質、沈着のプロセスの解明と、組成・分布・輸送のデータから植物、人間の健康への影響を明らかにすることを目的に平成20年度から24年度までに行われた科学研究費補助金新学術領域研究「東アジアにおけるエアロゾルの植物・人間系へのインパクト」の成果をまとめ、広く一般に公開してその成果を周知させるとともに、幅広い領域の人々に利用してもらうことを本研究の目的とした。
    本研究では研究成果報告会の開催と、雑誌体の報告集を発行することの２通りの手段により、上記目的の達成をめざした。
    （１）一般向けの研究成果報告会を平成25年10月23日に東京都府中市の府中グリーンプラザにおいて開催した。ここでは本領域において平成20年度から24年度まで毎年行ってきた全体会議シンポジウムのような研究者向けの難しい言葉ではなく、高校生以上程度の一般の市民が充分理解できるよう注意を払って報告を行った。
    （２）研究成果の印刷体によるとりまとめは、日本エアロゾル学会の機関誌「エアロゾル研究」の特別号として発行することとし、社会への発信を含めた取り組みとして行った。
    これにより、本領域の研究成果を、その主題とするエアロゾルの研究者ほぼ全員に配布することができた。また通常の雑誌配布冊数より多く印刷し、エアロゾル学会非会員の植物や健康影響の分野の研究者にも配布した。またそれ以外の興味を持たれる研究者や市民にも入手可能となるよう、上記報告会の参加者には希望に応じて別途送付するとともに、エアロゾル学会を通じて本特別号の内容をJ-STAGEによって、web公開した。
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Tokyo University of Agriculture and Technology, 20120001
  • Understanding of the formation mechanisms of secondary organic aerosols by real-time measurements of their precursors
    Grants-in-Aid for Scientific Research
    2008 - 2012
    HIROKAWA Jun; INOMATA Satoshi; TAKAHASHI Kenshi
    Atmospheric oxidation of volatile organic compounds (VOCs) and subsequent reactions can produce low-volatility species which contribute to secondary organic aerosols (SOAs). In this study, reaction probabilities for elementary steps were determined and new chemical mechanisms of SOA formation were proposed based on gas- and aerosol-phase analysis of reaction products.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), Hokkaido University, 20120003
  • Measurements of nitrous acid concentration in the atmosphere using chemical ionization mass spectrometry
    Grants-in-Aid for Scientific Research
    2008 - 2010
    HIROKAWA Jun; MAFUNE Fumitaka
    Chemical ionization mass spectrometry was applied to the measurement of nitrous acid in the atmosphere. By optimizing reaction conditions for the chemical ionization and increasing the signal intensity of the primary ion, the limit of detection of 40 pptv can be obtained for an integration time of 1 minute. Possibility of the interferences from other atmospheric species was investigated by laboratory experiments and ab initio calculations. The interference from nitrogen dioxide in humid air was experimentally quantified. Preliminary measurements of nitrous acid were carried out in Sapporo city.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 20310001
  • Solvation structure of iodide on an aqueous solution surface and relevant heterogeneous chemical reactions
    Grants-in-Aid for Scientific Research
    2007 - 2009
    MAFUNE Fumitaka; HIROKAWA Jun; MIYAJIMA Ken
    Specific interaction of ions with solvent molecules on a solution surface causes characteristic solvation structures of ions. As solvation structures of halogen ions relate to the heterogeneous chemical reaction of OH radicals in the atmosphere, it is very important to elucidate the solvation structures. First-principles molecular dynamics simulation suggests that iodide ions tend to locate near the surface, whereas chloride ions prefer to be located deep inside the surface.
    We measured absorption spectrum of iodide ions in the vicinity of the aqueous solution surface : When a NaI aqueous solution is irradiated with a UV light, I- is excited to the CTTS (charge transfer to solvent) state. Then, it is further excited by absorbing another photon and the electron is released from I-. As the electron escape depth from the solution surface is in the order of 1nm, we are able to detect electrons originating from I- located in the vicinity of the surface by the gas phase method. We measured a signal intensity of the electrons as a function of the wavelength of the laser, and found out that I- tends to be located inside the solution at the lower NaI concentration, starting to appear on the surface at the higher NaI concentration. We examined the solvation structures of Na^+ by detecting ions from the surface. It was found that Na^+ tends to be inside the solution regardless of the concentration of NaI.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), The University of Tokyo, 19350005
  • Ice nucleation activity of organic particles in cloud processes : Analysis using a thermal diffusion chamber
    Grants-in-Aid for Scientific Research
    2006 - 2008
    MOCHIDA Michihiro; HIROKAWA Jun; NAKATSUBO Shunichi; SHIGEI Akio
    大気エアロゾル粒子やそのモデル粒子の氷晶形成能力を測定する目的で、熱拡散チェンバの立ち上げを進めた。また、熱流体解析ソフトウェアを用いて、エアロゾル導入部の性能の検討や、先行研究で報告のある空気の速度・水蒸気の飽和度などの計算を行った。さらに、実際の装置を用いて温度制御や氷膜の生成等について検討を進めた。本研究は期間途中で終了となったが、熱拡散チェンバを用いる実験は、関連した研究において継続される予定である。
    Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (A), Nagoya University, 18684031
  • 化学イオン化質量分析法を用いたエアロゾル前駆気体濃度測定装置の開発
    科学研究費助成事業
    2004 - 2005
    廣川 淳
    無機エアロゾル二次生成過程の重要な前駆気体であるアンモニアおよび塩化水素の大気中濃度を高感度かつ高速に測定するため、化学イオン化質量分析法を用いた装置の開発を計画した。アンモニアはプロトン親和力が高いことから、プロトン付加したエタノールクラスターイオンを試薬イオンとして用い、そこからの発熱的なプロトン移動反応を利用することにより、アンモニアをイオン化することを考えた。しかし、実大気における試験的な測定の結果、試薬イオンが大気中の他の成分との反応により大幅に減少し、アンモニアの濃度測定が干渉されることがわかった。そこで、プロトン親和力がアンモニアとエタノールの間に位置するアセトンのプロトン付加クラスターを新たに試薬イオンとして用い、アンモニアの化学イオン化を試みた。実大気測定の結果、濃度1ppbvレベルのアンモニアを検出可能であること、および他成分による干渉がないことが示された。また、大気中のアンモニア濃度の変化に対して、1分以内の時間応答を有することも確かめることができた。一方、塩化水素は、ハロゲン負イオンに対する親和力が高いことから、SO_2Cl^-を試薬イオンとした塩化物イオン移動反応による化学イオン化を計画した。標準ガスを用いた実験から、試薬イオンと塩化水素とのイオン-分子反応によりClHCl^-イオンが生成し、その信号強度は導入した塩化水素濃度と直線関係にあることが見出された。この直線の傾きから感度は、200〜300cps(counts per second)/ppmvと見積もられた。
    日本学術振興会, 特定領域研究, 北海道大学, 16030201
  • Studies on strategic control of photochemical oxidants in mega-cities
    Grants-in-Aid for Scientific Research
    2002 - 2004
    KONDO Yutaka; KAJII Yoshizumi; KOIKE Makoto; KITA Kazuyuki; TAKEGAWA Nobuyuki; HIROKAWA Jun
    We have developed instruments for precise measurements of ozone precursors (NOx,HNO_3,PAN,VOCs, and CO), OH and HO_2 radicals, and actinic flux. Measurement campaigns using these instruments were conducted in different seasons in 2003-2005. Especially, in July-August 2004, intensive measurements were made at two sites ; one in Tokyo and the other in Kisai-city in Saitama. At the same time, aerosol chemical composition at each size range was measured using an Aerodyne Aerosol Mass Spectrometer. Air mass which left Tokyo reaches Saitama in the afternoon, providing ideal conditions for investigationg chemical processes during transport. In mid-August, sea-land breeze developed under the influence of stable high pressure system. Under these conditions, O_3 reached high levels in northern Tokyo around 1300 LT. This O_3 levels further increased while the air mass was transported to Saitama by sea breeze. During the transport, NOx oxidation and O_3 formation occurred simultaneously. Organic aerosol was observed to be formed efficiently under high O_3 conditions. 3D-CTM has been developed taking into account the chemical and transport processes. This model well reproduces O_3 and precursors in Kanto area. By this model, it is indicated that O_3 was produced within a few hours near noon.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), The University of Tokyo, 14208061
  • Study on atmospheric chemical mechanisms related to each hemispherical atmospheric OH trend derived from AGAGE observation
    Grants-in-Aid for Scientific Research
    2002 - 2003
    KUTSUNA Shuzo; HIROKAWA Jun; TAKAMI Akinori
    When the atmospheric OH concentration is inferred from long-term ground-based observatory data on atmospheric concentration of CH_3CCl_3 in the AGAGE, a gas-phase reaction with OH is considered a main atmospheric sink of CH_3CCl_3,and photolysis and dissolution into sea water are regarded as minor sinks of CH_3CCl_3. In this study, an additional sink of CH_3CCl_3, that is, heterogeneous decomposition on clay minerals, was examined. The reaction of CH_3CCl_3 on 25 standard day minerals was examined with a closed-circulation reactor and found that the decomposition of CH_3CCl_3 proceeded through CH_3CCl_3→CH_2=CCl_2+HCl at 313 K for most of the clay minerals examined (γ〜10-9).
    The uptake coefficients (γ) of NO_2 and SO_2 to the aqueous surface were measured using the impinging flow apparatus. The aqueous solution including H_2O_2 or C_6H_4(OH)_2 gave larger γ values of NO_2 than pure water, because aqueous phase reaction of NO_2 with the solutes increased the γ value. We cannot observe any increase in the γ values of NO_2 or SO_2 when quasi-seawater was examined, influence of aqueous phase chemical reaction on the γ value of OH radicals was estimated.
    The influence of water vapor on determination of Br_2 with a chemical ionization mass spectrometer was studied. Since a reagent associated with water to form hydrated ions, the mass peak of Br_2 ion could not be normalized with the peak of the reagent ion. However, we have indicated that it can be normalized with the peaks of both the reagent and the hydrated ions. A falling film absorber was prepared to measure the uptake coefficients (γ) to liquid surfaces and it was applied to measurement of γ of Br_2 to the water surface. Comparison of the measurement with the simulated calculation revealed that the aqueous phase reaction was a limiting-step in the uptake of Br_2 to water.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), National Institute of Advanced Industrial Science and Technology (AIST), 14580558
  • 化学イオン化質量分析計を用いた海洋大気中の次亜臭素酸濃度の測定
    科学研究費助成事業
    2001 - 2002
    廣川 淳
    化学イオン化質量分析計を用いて、次亜臭素酸HOBrを高感度かつ選択的に検出、測定するための化学イオン化スキームとして、フッ素負イオンF^-及び塩素負イオンCl^-を試薬イオンとして用いたハロゲン負イオン付着反応の有用性を検討した。フッ素負イオン及び塩素負イオンはそれぞれ三フッ化窒素NF_3及び塩化メチルCH_3Clを試薬気体として用いるが、これらからの負イオン生成法として、コロナ放電イオン化及び放射線源を用いた低速電子付着イオン化の2つの手法を取り上げ、その有効性を実験的に調べた。フッ素負イオンの場合は、コロナ放電イオン化によりフッ素負イオンに加え、フッ化水素が生成し、これがフッ素負イオンに付着したクラスターイオンの生成が質量分析計により確認された。これはNF_3の放電により、フッ素負イオンと同時にフッ素原子が多量に生成し、これが周囲大気中に微量に存在する水蒸気から水素原子を引き抜くことにより、フッ化水素を生成しているものと考えられ、化学イオン化の試薬イオン生成法をしては不適当であると判断された。一方、放射線イオン源を用いた場合は、フッ化水素付着クラスターイオンの生成は見られず、フッ化物負イオンの質量ピークのみが観測された。また、塩素負イオンの場合は、コロナ放電イオン源、放射線イオン源ともに塩素負イオンとそれに水蒸気が付加したイオンが観測され、塩化水素の副生成は見られなかった。以上の実験結果より、化学イオン化の試薬イオンとしてフッ素負イオン、塩素負イオンを生成する場合、コロナ放電イオン源に比べ放射線イオン源の方が適していると結論付けることができた。
    日本学術振興会, 若手研究(B), 東京大学, 13780414
  • 海塩粒子とオゾンの不均一化学反応の研究
    科学研究費助成事業
    1999 - 2000
    廣川 淳
    クヌッセンセル法を用い、海塩粒子のモデル化合物に対するオゾン(O_3)の取り込み過程を調べた。特に、海塩粒子中に含まれる微量金属イオンが不均一反応に及ぼす影響を調べるため、塩化第二鉄(FeCl_3)をごく微量に含んだ塩化ナトリウム(NaCl)及び合成海塩粒子をモデル化合物として、これら固体粒子表面へのオゾンの取り込み係数の測定、及び取り込みにより生成する化合物の同定を行った。FeCl_3を微量に含んだNaClの系では、Fe/Na比が0.1%、0.5%、1%の3種類の試料を調製し、これらへのオゾンの取り込み係数を測定した結果、Fe/Na比によらず(1.6-1.9)×10^<-2>という値が得られた。また、オゾンの取り込みに伴い塩素分子(Cl_2)の生成が観測されたが、その生成収率はFe/Na比に依存し、Fe/Na比=0.1%では検出限界以下であったのに対し、Fe/Na比=0.5%、1%でそれぞれ27%、47%であった。一方、合成海塩粒子にFeCl_3を微量に混合させた系では、同程度の取り込み係数1.9×10^2が得られたが、塩素分子の生成はみられず、かわりに臭素分子(Br_2)の生成が観測された。これは、合成海塩粒子に含まれる臭化物イオンが塩化物イオンに比べ反応性が高いため、まず臭素分子が生成したものと考えられる。これらの結果は、陸起源の土壌粒子などとの内部混合によりFe^<3+>イオン濃度が高くなった海塩粒子において、オゾンとの不均一反応が促進されることを示唆している。特に、大気寿命の長い(数日以上)、粒径の小さい粒子では、臭化物イオンがまず欠乏する結果、オゾンの取り込みにより塩素分子が生成することが予想され、これまで特定されなかった、海洋境界層における塩素分子発生源としてこの反応のはたらく可能性が高い。
    日本学術振興会, 奨励研究(A), 東京大学, 11780379
  • Studies on chemistry and cycles of halogens in the troposphere
    Grants-in-Aid for Scientific Research
    1998 - 2000
    KAWAMURA Kimitaka; HIROKAWA Jun; YOKOUCHI Yoko; TANAKA Shigeru; NAKATSUKA Takeshi
    In this program, we conducted several projects. They include (l) measurements of inorganic halogens and their atmospheric behaviors, (2) development of halogen measurement and its application to the atmosphere, (3) atmospheric behaviors of halogenated volatile hydrocarbons, (4) halogenated organics in aerosols and analysis of organic aerosols, (5) carbon isotopic analysis of non-methane hydrocarbons, (6) dynamics and interaction of halogens in air/water interface, and (7) formation mechanism and cycles of biogenic halocarbons.
    We made a new analytical system to measure hologen gases by using scrubber technique. By using this method, a formation of halogen gases from the sea salt particles was observed. We also observed a decrease in the concentration of Cl^2 and an increase of HCl gas in daytime in the marine atmosphere. A chemical ionization mass spectrometer that was designed for the measurement of Br^2 and Cl^2, has been made in this study. Using this instrument for laboratory experiment, we observed the formation of Br^2 gas on the surface of sea salt particles as a result of Cl uptake. We also confirmed the release of halogen gases from the sea salts by the reaction with ozone. Seawater and air samples collected from the Pacific Ocean were analyzed for holocarbons using a purge and trap GC/mass spectrometry. We found a seasonal change of halogen compounds with maxima in August/September in the western North Pacific. In the marine aerosols, we identified, for the first time, halogenated organic acids and aldehydes, including bromosuccinic and chlorosuccinic acids. The former acid showed higher concentrations in the western North Pacific near Asia continent, whereas the latter increased in the central Pacific. Based on the observations over the Pacific, we proposed a photochemical formation model for the newly rescovered halogenated organic compounds and an evolution model of organic aerosols.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research on Priority Areas (A), HOKKAIDO UNIVERSITY, 10144101
  • INSTRUMENTAL DEVELOPMENT OF ULTRA-HIGH PERFORMANCE NOx ANALYZER USING LASER INDUCED FLUORESCENCE TECHNIQUE
    Grants-in-Aid for Scientific Research
    1997 - 1999
    KAJII Yoshizumi; YOSHIZAWA Hitoshi; HIROKAWA Jun
    ULTRA HIGH PERFORMANCE NOx ANALYZER USING LASER INDUCED FLUORESCENCE TECHNIQUE WAS DEVELOPED. THIS INSTRUMENT COSISTS OF DIODE LASER PUMTPED Nd:YAG LASER, CORRECTION SYSTEM OF LASER FLUCTUATION, LIF CELL, COLLECTION OPTICS FOR LIF, PHOTON COUNTING SYSTEM, VACUUM SYSTEM, AND PERSONAL COMPUTER FOR SYSTEM CONTROL AND DATA ACQUSITION. WE OPTIMIZED THESE COMPONENTS AND MADE EFFORTS FOR DOWN-SIZING THE INSTRUMENT. THE INSTRUMENT CAN MEASURE AS LOW AS 3.8 PPTV OF NOィイD22ィエD2 FOR 1 MIN. INTEGRATION. WE BROUGHT THIS INSTRUMENT TO THE OKINAWA ATMOSPHERIC STATION WHERE AIR IS VERY CLEAN AND NOx LEVEL IS VERY LOW. WE SUCCEDED TO MEASURE CLEAN HUMID MARIN NOx CONCENTRATION. INTER-COMPARISON WITH DIFFERENT PRINCIPLE OF TECHNIQUE AND GOT QUITE GOOD RESULT AND WE CONCLUDED THIS INSTRUMENT IS PRACTICALLY QUITE USEFUL AND RELIABLE ENOUGH TO MEASURE REMOTE CLEAN AIR SAMPLE.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), THE UNIVERSITY OF TOKYO, 09558066
  • SYNTHETIC OBSERVATIONAL STUDY ON OH AND OTHER REACTIVE TRACE GASES TO TEST THE THEORY OF ATMOSPHERIC PHOTOCHEMISTRY
    Grants-in-Aid for Scientific Research
    1997 - 1999
    KAJII Yoshizumi; BANDOW Hiroshi; HIROKAWA Jun
    DEVELOPMENT OF INSTRUMENT TO MEASURE THE CONCENTRATION OF HOX RADICALS IN AMBIENT AIR BY USING LASER INDUCED FLUORESCENCE TECHNIQUE WAS PERFORMED. TO GET ADVANCED KNOWLEDGE OF ATMOSPHERIC CHEMISTRY SYNTHETIC OBSERVATIONAL STUDIES OF OH AND OTHER REACTIVE TRACE GASES IN REMOTE ATMOSPHERE WERE CARRIED OUT IN 1998 AT OKI ISLAND AND IN 1999 AT OKINAWA ISLAND. IN OKI OBSERVATION WE FOUND NEW HOX RADICAL SOURCE IN NIGHTTIME AS OZONOLYSIS REACTION WITH BIOGENIC OLEFINS. IN OKINAWA WE SUCCEEDED TO MEASURE OH RADICAL AND AVERAGE CONCENTRATION IN NOON TIME WAS DETERMINED TO BE CA. 3 X 10ィイD16ィエD1 RADICALS CMィイD1-3ィエD1. OZONE PRODUCTION POTENTIAL IS FOUND To BE QUITE HIGH EVEN IN THE CLEAN REMOTE ISLAND LIKE OKINAWA. THERE ARE CONSIDERABLE AMOUNTS OF OZONE PRECOURSORS LIKE BIOGENIC OLEFINS AND ALSO BIGENIC NOx. OZONE PRODUCITON RATE IN NOON TIME WAS ESTIMATED TO BE 4 PPPB DAYィイD1-1ィエD1.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), THE UNIVERSITY OF TOKYO, 09480115
  • Development of Liquified Air/Fourier Transform Infrared Spectroscopic Method for Simultaneous Measurement of Atmospheric Trace Gases
    Grants-in-Aid for Scientific Research
    1995 - 1996
    AKIMOTO Hajime; KAWASAKI Masatsugu; KAJII Yoshizumi
    A novel method for simultaneous measurement of atmospheric trace gases using liquified air/Fourier transform infrared spectroscopy has been developed. The equipment consists of Fourier transform infrared spectrometer, transfer optics and a cryostat containing optical light pipe. The cryostat consists of helium refrigerator, and a light pipe (4 mm i. d. and 20 cm long, gold coated). The air introduced into the cryostat was liquified by the helium refrigerator and the liquified air was introduced into the light pipe. Infrared spectrum of the liguified air was taken by the FTIR spectrometer with a resolution of 1 cm^<-1>.
    Carbon monoxide (1.6 ppm in synthesized air) gave an absorption band at 2140 cm^<-1> with a band-width of 20 cm^<-1>. Methane (10 ppm in synthesized air) gave absorption band at 1305 and 3016 cm^<-1> with band-width of 10 and 20 cm^<-1>, respectively. Those bands were well separated from large saturated peaks of CO_2 and H_2O contained in air and found to be used for quantitative measurement of CO and CH_4. Detection limit estimated from S/N ratio of 3 was 35 ppb for CO,and 23 and 40 ppb for CH_4 using the bands of 1305 and 3016 cm-1, respectively. These detection limit is low enough compared with the typical atmospheric concentration of CO (100-500 ppb) and CH_4 (1.7-2.0 ppm). The proposed method was found to be applicable for the detection of these trace gases in the atmosphere.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Research Center for Advanced Science and Technology, University of Tokyo, 07558193
  • DEVELOPMENT OF DETECTION METHOD FOR MEASURING AMBIENT NO CONCENTRATION USING HIGH SENSITIVE LASER SPECTROSCOPIC TECHNIQUE
    Grants-in-Aid for Scientific Research
    1995 - 1996
    KAJII Yoshizumi; HIROKAWA Jun
    we designed and constructed vacuum chamber and vacuum system for measuring ambient NO concentration. The laser system of tunable dye laser pumped by 3rd harmonic of pulsed nd : YAG laser was constructed. The out-put of dye laser was doubled to excite NO molecule into single ro-vibronic level. The analysis of rotationnal temperature was done to determine rotational temperature to be 25 K under X/D of 70. we reconfirmed resonance enhanced two photon ionization (RETPI) process rom the laser power dependence experiment showing index of 1.75. we employed ion counting system for detection of ion signals to increase S/N ratio. we found almost of two order of magnitude improvement of sensitivity by replacement of detection system from analog-to-digital operation to ion counting operation. we confirmed linear response of ion signal with NO concentration up to 200 ppb. In the chemical. interference of NO_2, the sensitivity of NO_2 is ca.2% compared to that of NO.This shows the improvement of selectivity by the cooling process. The limit of detection was estimated to be 16 pptv with an integration time of 1 min.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), RESEACH CENTER FOR ADVANCED SCIENCE AND TECHNOLOGY,THE UNIVERSITY OF TOKYO, 07454147
  • Development of LIF instrument for Measuring Tropospheric Hydorxyl Radicals and Verification of Photochemical Theory
    Grants-in-Aid for Scientific Research
    1994 - 1996
    AKIMOTO Hajime; HIROKAWA Jun; KAJII Yoshizumi
    We designed and constructed vacuum chamber and vacuum system for measuring ambient OH radical concentration. To detect OH radical free from O_3 chemical interference the Low Pressure Laser Induced Fluorescence technique was employed. The lasers system of tunable dye laser pumped by 2rd harmonic of pulsed Nd : YAG laser which was pumped by diode laser was constructed. The out-put of dye laser was doubled to excite OH radical into single ro-vibronic level of the first doublet excited state (A^2SIGMA^+v''=0). LIF singnals of OH radicals were collected by lens system and detected by MCP gated PMT after interference fillter of 308 nm. Photon counting technique was employed to improve S/N ratio. To determine the absolute concentration of OH radicals, two techniques were employed for calbration for the LIF instrument. One is chemical titration method to control radical concentrations ; the reaction H + NO_2*OH + NO was used. Using this reaction and assuming that this reaction is fast enough and chemical loss of OH radical is negligible, concentration of OH raical was controled. The other method employed was optical absorption technique. Multi-pass absorption (base path=1 m ; 100 times) and VUV photolysis of water vapor were used to calbrate the instrument. From these independent techniques, sensitivity of the instrument was determined to be 5 * 10^<-9> and 9 * 10^<-9>/cps mW^<-1>/ (OH cm^<-3>). This good agreement indicates our system has enough precision. Limit of detection (LOD) was estimated to be 7 * 10^8 radicals cm^<-3> under present condition. It is found that this instrument has enough potential for measuring ambient HO_2 radical.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), RESEARCH CENTER FOR ADVANCED SCIENCE AND TECHNOLOGY,THE UNIVERSITY OF TOKY, 06403031
  • 大気中におけるHOxラジカル測定手法の高度化に関する研究
    科学研究費助成事業
    1994 - 1994
    秋元 肇; 廣川 淳; 梶井 克純
    本年度からレーザー誘起蛍光法(LIF)に基づく対流圏OHラジカル測定装置の高度化に関する研究に着手した。
    1.レーザー光源
    本装置は将来実用的に野外観測使用することを目的としている。従って本研究に用いられるレーザー光源としては、個々の仕様を満たしていることとともに、操作の安定性に優れかつコンパクトであることが必要条件とされる。本研究では対流圏OH測定用としては世界で初めて、最近開発された半導体レーザー励起のYLFレーザーを励起光源とする小型色素レーザーを用いることとし、必要仕様のシステムを特注した。得られたレーザーシステムについて調整の結果306nmにおいてくり返し周波数1kHz、パルス幅数nsec、パルスあたりエネルギー数μJ、波長幅約0.1cm-1のレーザー光を得ることができた。
    OHラジカル参照セル
    レーザーの発振波長をOHラジカルの1本の回転線にロックするための、OHラジカル参照セルを製作した。参照セルとしては、セル内を室内空気を数torrの圧力で流通させ加熱したアルメル線のフィラメント上での水蒸気の熱分解によってOHラジカルを生成させ、その中をレーザー光を通過させて得られるLIFシグナルを測定するための光電子増倍管を組み込んだものとした。
    3.LIF測定用多重反射セル
    励起用レーザー光を球面鏡の間で多重反射させることによって励起効率を高め、これと直角の方向からレンズを用いてマルチチャンネルプレート(MCP)上に蛍光を集光する大気中OHラジカルのLIF測定用セルを設計、製作した。多重反射鏡システムとしては従来通常用いられている3枚鏡ホワイトセルの代わりに、2枚鏡システムを採用し調整の簡単化を図った。
    日本学術振興会, 重点領域研究, 東京大学, 06228208
  • 対流圏大気における化学反応過程の解明
    Competitive research funding