Differential Cross Sections for Ionization of Water Vapor by High-Velocity Bare Ions and Electrons

A semiempirical model of single differential cross sections (SDCS) for ionization of water vapor by fast electrons and bare ions is presented. At low secondary-electron energy, the model is based on an asymptotic expansion of the first Born approximation with coefficients, that are independent of projectile properties, evaluated from experimental photoabsorption and protonimpact ionization data. As the secondary-electron energy increases, the model converges to a binary-encounter approximation. Comparisons with measured differential, total, and dissociative cross sections for ionization of water by fast electrons are used to test the model. For primary electrons with energy greater than about 500 eV, agreement with these data is generally within experimental uncertainty; however, some discrepancies of uncertain origin exist. The Journal of Chemical Physics is copyrighted by The American Institute of Physics. History: Received 8 August 1986; accepted 18 September 1986 Permalink: http://link.aip.org/link/?JCPSA6/86/157/1 Differential cross sections for ionization of water vapor by high-velocity bare -