High resolution study of photoionization processes in O2

Abstract

Relative photoionization efficiency curves were determined for the production of O⁺₂, O⁺, and O⁻ from molecular oxygen in the wavelength region of the helium continuum. The photoionization efficiency curve for O⁺₂, determined at a wavelength resolution (FWHM) of 0.07 Å throughout most of the region from 1030–580 Å, shows rotationless autoionization structure which is broadened due to the processes of predissociation and/or autoionization. The photoionization effciency curves for fragment ions from ion pair formation and from dissociative ionization were determined at wavelength resolutions of 0.07 and 0.15 Å, respectively. The data show considerable autoionization structure and provide information about the mechanisms for these dissociation processes. The ion pair photoionization efficiency curve shows steplike structure at threshold resulting from direct ionization from individual rotational levels of the ground state of O₂. A value of the electron affinity of atomic oxygen of 1.462±0.003 eV was determined from the wavelength corresponding to ionization from the O₂(³Σ⁻_g, v=0, J=1) ground state.