Simultaneous ionization and excitation of Ar by electrons with particular attention to configuration-interaction effects

Absolute apparent cross sections for electron impact excitation of the $4s^{\prime }$, $5s$, $3d$, $4d$, $5d$, $3d^{\prime }$, and $4d^{\prime }$ configurations of ${\mathrm{Ar}}^{+}$ from the ground state of Ar are presented by studying the vacuum uv photon decay of the states. The high-energy behavior of the excitation functions is demonstrated to reflect the two-electron nature of the initial excitation. Where cascade can be satisfactorily taken into account, excitation of states with the same orbital angular momentum and multiplicity is shown to be according to their statistical weights. Some significant discrepancies are exposed between theoretically calculated and experimentally measured relative transition probabilities. Configuration-interaction effects are demonstrated to exist in a number of instances and are quantitatively investigated for the ${}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}$ states.