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 and Radiological Science and Technology.
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Linear energy transfer (LET) dependence of yields of O2-dependent and O2-independent hydrogen peroxide (H2O2) in water irradiated by ionizing radiation was investigated. The radiation-induced hydroxyl radical (•OH) generation in an aqueous solution was reported to occur in two different localization densities, the milli-molar (relatively sparse) and/or molar (super-dense) levels. In the milli-molar-level •OH generation atmosphere, •OH generated at a molecular distance of ~7 nm are likely unable to interact. However, in the molar-level •OH generation atmosphere, several •OH were generated with a molecular distance of 1 nm or less, and two •OH can react to directly make H2O2.
An aliquot of ultra-pure water was irradiated by 290-MeV/nucleon carbon-ion beams at the Heavy-Ion Medical Accelerator in Chiba (HIMAC, NIRS/QST, Chiba, Japan). Irradiation experiments were performed under aerobic or hypoxic (<0.5% oxygen) conditions, and several LET conditions (13, 20, 40, 60, 80, or >100 keV/μm). H2O2 generation in irradiated samples was estimated by three methods. The amount of H2O2 generated per dose was estimated and compared.
O2-independent H2O2 generation, i.e. H2O2 generation under hypoxic conditions, increased with increasing LET. On the other hand, the O2-dependent H2O2 generation, i.e. subtraction of H2O2 generation under hypoxic conditions from H2O2 generation under aerobic conditions, decreased with increasing LET. This suggests that the super-dense •OH generation is positively correlated with LET. High-LET beams generate H2O2 in an oxygen-independent manner.
Effects of LET on oxygen-dependent and-independent generation of hydrogen peroxide in water irradiated by carbon-ion beams
