Radiolysis of water vapour by low-energy heavy ions

Abstract

Radiolysis of water vapour at low pressure (≤ 10^–4 torr) has been studied using ion beams from an electromagnetic isotope separator and a 600 keV ion accelerator. Ions used were He⁺, Ne⁺, Ar⁺, K⁺, Kr⁺, and Xe⁺, at 30, 60, and 500 keV. Radiolytic products have been investigated both directly in the gas phase by means of emission spectroscopy and indirectly with e.s.r. and chemical analysis of deposits formed by condensing the irradiated vapour. H, OH, O⁺, and OH⁺ are detected in the gas phase. Hydroxyl radicals are present in deposits formed at temperatures at or below –180°C, hydroperoxy radicals in all investigated deposits, but no electrons are detected. Relative and absolute cross-sections for generation of hydroxyl radicals with 60 keV inert gas ions are measured and compared with theoretical calculations for the reaction ion + H₂O → OH + H.