Online analysis and yield determination of H produced in water radiolysis with Co -rays and C ion beams

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

Main initial products of water radiolysis are e and OH, which go through intraspur/track reactions in the time regime from ps to s, leading to production of HO and H. Among the main products, only H is not soluble in water and difficult to be accurately quantified. H 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. Therefore, an online analysis apparatus of gaseous products arising from liquid samples has been developed to measure H production from water. In this work, at first accuracy and sensitivity of the apparatus were improved, and then, H yields were measured as a function of concentration of the nitrate anion, which is a scavenger not only for e but also for the pre-solvated electron (e). Figure shows G(H) measured in this work in comparison with reported values. Well-established primary G value for Co -irradiation, 0.46 (100 eV), is obtained at low NO concentrations. Our data with Co -irradiation were in good agreement with the reported values. In the cases of C ion irradiations G(H) values increased with increasing LET due to increasing significance of intratrack reactions. Further discussion on H production in fast process before 1 ps necessitate measurements of G(H) at other NO concentrations and with the usage of other scavengers of e and e.