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Report No.

Online analysis and yield determination of H$$_{2}$$ produced in water radiolysis with $$^{60}$$Co $${gamma}$$-rays and C ion beams

Yamashita, Shinichi; Katsumura, Yosuke; Murakami, Takeshi*

Main initial products of water radiolysis are e$$^{-}$$$$_{aq}$$ and $$^{bullet}$$OH, which go through intraspur/track reactions in the time regime from ps to $${mu}$$s, leading to production of H$$_{2}$$O$$_{2}$$ and H$$_{2}$$. Among the main products, only H$$_{2}$$ is not soluble in water and difficult to be accurately quantified. H$$_{2}$$ also tends to leak even from a very small crevice where other gases do not leak. It is necessary to pay attentions to leakage and equilibrium between liquid-gas phases when ones want to accurately quantify H$$_{2}$$. Therefore, an online analysis apparatus of gaseous products arising from liquid samples has been developed to measure H$$_{2}$$ production from water. In this work, at first accuracy and sensitivity of the apparatus were improved, and then, H$$_{2}$$ yields were measured as a function of concentration of the nitrate anion, which is a scavenger not only for e$$^{-}$$$$_{aq}$$ but also for the pre-solvated electron (e$$^{-}$$$$_{pre}$$). Figure shows G(H$$_{2}$$) measured in this work in comparison with reported values. Well-established primary G value for $$^{60}$$Co $${gamma}$$-irradiation, 0.46 (100 eV)$$^{-1}$$, is obtained at low NO$$_{3}$$$$^{-}$$ concentrations. Our data with $$^{60}$$Co $${gamma}$$-irradiation were in good agreement with the reported values. In the cases of C ion irradiations G(H$$_{2}$$) values increased with increasing LET due to increasing significance of intratrack reactions. Further discussion on H$$_{2}$$ production in fast process before 1 ps necessitate measurements of G(H$$_{2}$$) at other NO$$_{3}$$$$^{-}$$ concentrations and with the usage of other scavengers of e$$^{-}$$$$_{aq}$$ and e$$^{-}$$$$_{pre}$$.



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