量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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Hydrogen radicals (•H) generated during irradiating to aqueous solutions were quantified by an electron paramagnetic resonance (EPR) spin-trapping technique using a spin-trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The •H could be generated by reaction of hydrated electron (eaq) and hydrogen ions (H+), which were generated simultaneously with hydroxyl radical (•OH) from ionized water (H2O+). Therefore, the local density of •H may be the similar amounts of •OH.
A concentration series of DMPO aqueous solutions (0.49 mM 〜 1700 mM) was prepared. The sample solutions were irradiated 32 Gy of 20 keV/μm, or 80 keV/μm carbon-ion beam. Signal intensities of DMPO-H caused in the sample were measured by X-band EPR spectrometer. The profiles observed by plotting concentrations of DMPO-H against the DMPO density (reciprocal of the intermolecular distance of DMPO) were analyzed.
When X-ray or carbon-ion beam was irradiated to DMPO aqueous solutions under aerobic condition, the profile of DMPO-H generation showed 2-phase and have an inflection point at 160 µm-1 or 125 µm-1, respectively. The intermolecular distance of •H generated by X-ray or carbon-ion-beam in water was estimated as 6.3 or 8.0 nm, respectively. Under hypoxic condition, DMPO-H generation profile showed plateau over the DMPO density more than 100 µm-1 and the molecular distance of •H was estimated as 10 nm for either X-ray or carbon-ion beam irradiation.
重粒子線が水溶液中で生成する水素ラジカルの定量
