The nature of the reducing species in the radiolysis of acidic aqueous solutions at high intensities

Abstract

The radiolysis of acidic aqueous solutions with single 1.4 μsec pulses of 13 MeV electrons from a linear accelerator has been studied, over the intensity range 1.56 × 10 19 → 1.23 × 10 22eV.1 −/pulse. The effect of hydrogen peroxide, oxygen and cupric ion on G(H 2) [the hydrogen yield] was noted. Up to an intensity of 6.24 × 10 19 eV.1 −1/pulse the scavenging action of the solutes on the G(H 2) can be explained in terms of H atoms and the rate constants associated with H atoms e.g. 2 H+H = 2 × 10 10 M −1sec −1 etc. At higher intensities the scavengers become mmore effective in decreasing the G(H 2). At thesehigh intensities more hydrogen peroxide was needed to produce the same percentage lowering of G(H 2) when trains of pulses were used instead of the normal single pulse. This was interpreted in terms of a species being produced in one pulse that lived for long enough to contribute to a following pulse. It is postulated that at intensities greater than 6.24 × 10 19 eV. 1 −1/pulse (1.4 μsec pulse) the predominant reducing species in H 2+ with k H 2 + +H 2+ < 5 × 10 5 M −1 sec −1. A discussion of the scavenging effect of hydrogen peroxide on the molecular hydrogen yield in Co 60 γ-radiolysis is included and attention is drawn to the similarity of the scavenging of the hydrogen gas precursor here to that at the highest intensity in the present work.