Studies on the molecular hydrogen formation (G_H2) in the radiation chemistry of aqueous solutions

G_H2 in the γ radiolysis of air-free 0.01, 0.1, and 1 M solutions of various cations and anions were measured. The rate constants of most of these ions with e_aq, at different ionic strength were directly determined by the pulse radiolysis technique. The effect of ionic strength on spurs reactions and on scavenging efficiency was studied. Difficulties previously observed, concerning the lack of correlation between k_eaq+s[S] and the scavenging efficiency of G_H2 were shown to be mainly due to ionic strength effects on k_eaq+s. Hence it is concluded that e_aq is the main precursor of G_H2 through the reactions: e_aq + H and e_aq + e_aq. It is suggested that G°_H2 and G°_H (which were proposed by Schwarz to be formed directly) result from spurs which are characterized by initially higher radical concentrations.