Concentration and incident energy dependences of transient species in water by H ion irradiation

Iwamatsu, Kazuhiro; Taguchi, Mitsumasa; Sugo, Yumi; Kurashima, Satoshi; Katsumura, Yosuke

This article reports a transient absorbance measurement system using energetic pulsed ions, and chemical reactions in aqueous NaBr solutions. Dose in pulse was evaluated by using GAF film dosimeter for the quantitative analysis of reactive species. NaBr aqueous solution was selected as a probe of chemical reactions in irradiated water samples because chemical reactions of Br with hydroxyl radicals produced by water radiolysis are well investigated by low LET radiation. The samples were irradiated with pulsed 20 MeV H ion provided by the AVF cyclotron. The formation and decomposition of Br were observed at 375 nm. The formation yield of Br slightly increased from 0.73 to 0.85 per 100eV absorbed energy with the increase in the concentration of NaBr from 1 to 1000 mM. The formation yield of Br for 1000 mM NaBr aqueous solution decreased from 0.85 to 0.27 per 100eV absorbed energy with the decrease in the incident energy from 19.4 MeV to 8.8 MeV, in other words increase of LET from 4.79 to 8.81 eV/nm.