Role of O⁻ in the Gas Phase Radiolysis of Alkane–Nitrous Oxide Mixtures

Abstract

WHEN an alkane gas is irradiated in the presence of nitrous oxide, nitrogen is formed. This has been shown to result from the dissociative capture of electrons by nitrous oxide¹ At constant dose rate the yield of nitrogen, G(N₂), obeys the expression expected for competition between electron capture and ion recombination. G(N₂)∞ is a constant, for a given hydrocarbon, and represents the yield of nitrogen when all electrons are captured. The fact that G(N₂)∞ is greater than the yield of electrons, G_e , calculated from the W value³, has been ascribed to the subsequent reaction of O⁻ with nitrous oxide^1,2. Evidence has been found, in the mass spectrometer, for reactions (2) and (3) (ref. 4). The relative rates of these reactions are not, however, reported. On the basis of the ethylene dosimeter^* (G(C₂H₄→H₂) = 1.31³), (G(N₂)∞ for the C₂, C₃ and C₄ alkanes is found to be 1.55 G_e (to be published). This can be explained by assuming a rate constant ratio, k₂/k₃, = 1.22.