Electron Yield in the ggr-Radiolysis of Water Vapor

Abstract

Nitrous oxide at low concentrations reduces the high yield of hydrogen from y-irradiated water vapor containing methanol from 8.9 per 100 electron volts absorbed to a plateau value of 5.9. This indicates that both electrons (yield 3.0) and hydrogen atoms (yield 5.4) are precursors to the hydrogen, the former being scavenged by nitrous oxide.The high yield of hydrogen, G(H2), produced when various additives are present during the y-irradiation of water vapor has been interpreted (1) in terms of reactions of H atoms:

The X-radiolysis of water vapor containing methanol. Effects of some electron and hydrogen atom scavengers

“…In water vapor containing nitrous oxide only, G(N,) = 3.0 -+_ 0.3 which was identified with the yield of scavengeable electrons (5,6) and is in reasonable agreement with the value calculated from the W-value in water vapor (20,21). Figures 2 and 3, however, show G(H2) falls by 2.2 i 0.6 when as little as 0.1 mole % nitrous oxide or sulfur hexafluoride is added to water vapor containing sufficient methanol to capture all available H atoms.…”

“…Increasing the concentration of nitrous oxide or sulfur hexafluoride from 0.1 to 1 mole % had no noticeable effect on G(H2); hence we can assume that 0.1 mole % is sufficient to capture all available electrons. I11 the absence of an electron scavenger, electrons are converted to hydrogen atoms via reaction [5] and the H atoms converted to H z via reaction [6]. These results therefore suggest that electroil -positive ion neutralization in water vapor containing methanol gives H atoms with a yield corresponding to G = 2.2 F 0.6, unless ion-ion neutralization results in the formation of H atoms.…”

“…In the presence of organic additives, however, the hydrogen yield greatly increases and a value for the total reducing species of G --8' has been obtained in H,O and D 2 0 containing various organic additives (2,4). The contributions of radical and ionic processes towards the yield of reducing species has been the subject of more recent publications (4)(5)(6). Irradiation of water vapor containing nitrous oxide gave G(N2) = 3.0, which is thought to represent the yield of scavengeable electrons in water vapor (5,6).…”

“…The contributions of radical and ionic processes towards the yield of reducing species has been the subject of more recent publications (4)(5)(6). Irradiation of water vapor containing nitrous oxide gave G(N2) = 3.0, which is thought to represent the yield of scavengeable electrons in water vapor (5,6). This value agrees well with the reduction in hydrogen yield AG(H,) --3 when nitrous oxide or sulfur hexafluoride is added to H 2 0 or D 2 0 vapor containing organic additives (4,5).…”

“…Irradiation of water vapor containing nitrous oxide gave G(N2) = 3.0, which is thought to represent the yield of scavengeable electrons in water vapor (5,6). This value agrees well with the reduction in hydrogen yield AG(H,) --3 when nitrous oxide or sulfur hexafluoride is added to H 2 0 or D 2 0 vapor containing organic additives (4,5). However, comparison of g(e) with the total yield of reducing species indicates that a major fraction does not have the electron as a pre-'A.E.C.L.…”