Dissociative Excitation of Water Molecule by Electron Impacts. I. General Survey and the Born Approximation

Abstract

Emission cross sections are evaluated in the Born approximation for the dissociative excitation processes of H 2 O by electron impacts, accompanied by the OH violet band, or the Lyman-α emission. Wave functions are from the Hatano-Nomura-Tanaka basis set as well as the Lin-Duncan set. The choice of wave functions strongly affects the magnitude of the cross section, but hardly affects its dependence on the incident electron energy. For the OH band, main contribution comes from the transition 3 a 1 →4 a 1 , and the electron exchange collision should be considered. For the Lyman-α emission, to which a number of superexcited states may correlate, it is found that the contribution of the transition 1 b 2 →6 a 1 (=4 s a 1 ) is dominant, while ones 1 b 2 →3 d a 1 , 3 d a 2 and 3 d b 2 the next. The calculated cross section is different from the experimental one at low energies of the incident electron, but is in accord with the experimental one at high energies. Alternative comparison is made on the optical and ...