Knowledge Bank

The Fano configuration interaction theory of autoionization is used to calculate partial photoionization cross-sections for production of diatomic ions in specific vibrational states. The anomalous vibrational distribution in the photoelectron spectrum of $O2$ excited with the neon resonance $line1$ is explained. The vibrational distribution in $O2+(X2\Pi g$) is calculated for both a uniform excitation continuum and for the solar vacuum-ultraviolet spectrum as an excitation source, with the contribution from autoionization of the upper states of the Hopfield bands of $O2$ explicitly included. About 5% of the $O2+$ produced by solar photoionization has more than 1 eV of vibrational energy.