Electron energy dependence of the kinetic energy and angular distributions of O+ from dissociative ionization of O2

Abstract

The electron energy dependence of the kinetic energy and angular distributions of O⁺ have been measured for the process of dissociative ionization of O₂. The kinetic energy distributions for energies above 0.5 eV are compared with other dissociative ionization measurements as well as results of dissociative photoionization and dissociative excitation by electrons leading to production of Rydberg excited neutral fragments. Angular distributions are interpreted in terms of symmetries of possible molecular ion states contributing to dissociation, and the results near threshold are compared with recent measurements of O⁻ from dissociative ion pair formation in O₂. Information about the states of excitation of the dissociation fragments as a function of ion energy is obtained from appearance potential measurements. The results indicate that predissociation may be important and that dissociative ionization of O₂ is in general a complicated process involving many ${\mathrm{O}}_2^{+}$ states.