Formation of ‘Molecular’ Hydrogen in the γ-Radiolysis of Water Vapour

Abstract

ATTEMPTS to measure initial yields from the radiolysis of pure water vapour have largely been vitiated by the presence of trace impurities and by the low concentration of products at steady state^1–3. While it has been demonstrated that the net production of hydrogen from the prolonged irradiation of water vapour is low^1,3, G(H₂) = 0.009 to 0.015, these measurements give no indication of the initial yield of hydrogen, or of the processes leading to its formation in the absence of added scavengers. A yield of ‘molecular’ deuterium, G(D₂)∼0.5, has been reported in the radiolysis of D₂O vapour in the presence of organic additives², and our present work confirms that a similar yield of hydrogen, G(H₂) = 0.47 ± 0.01, is obtained in the radiolysis of water vapour by a process which does not involve radical intermediates.