Nanosecond pulse radiolysis of aqueous solutions containing proton and hydroxyl radical scavengers

Source abstract

Abstract The time dependence of G(e+aq) in the early stages of the radiolysis of water has been investigated using nanosecond pulse techniques by studying the effects of added solutes which remove H3O+aq and OH. In pure water G(eaq) = 3.6 at 7.5 ns and 2.8 at 120 ns after a 5 ns electron pulse. Successive addition of 1 mol OH-/l and 1 mol CH3OH/l increased G(eaq) at the earlier time to 4.45 and 5.05 respectively. 1 mol I-/l had virtually no effect, and 1 mol Cl-/1 only a slight effect, on G(eaq) in neutral water, and 1 mol HCO2 /I had no effect at pH 14. From these results it is concluded that (i) G0eaq is not less than 5, (ii) G0H is close to zero, and (iii) in the expanding spurs eaq + eaq occurs between 10-8 and 10-7 s with AG(eaq) = 0.6, eaq + OH takes place between 10-9 and 10-8 s with AG(eaq) = 0.5, and eaq + H3O+aq is predominant between 10-11 and 10-9 s, is 80 % complete in 10-8 s and complete in 10-7 s with AG(eaq) = 1.1. Thus the data are in good agreement with the diffusion model and indicate that neither dry charge recombination nor direct excitation of water plays a significant role in the radiolysis of water.