Partial and differential photoionization cross sections of Cl and Br

Partial and differential cross sections are calculated for Cl and Br near the ${\mathit{nsnp}}^5$ thresholds. We compare our calculations with experiment, obtaining good agreement over part of the energy range. The autoionizing structure is well reproduced, but the slowly evolving direct contribution to the photoionization cross section does not have the correct shape. Most of the discrepancies with experiment in the autoionizing part of the spectrum appear to derive from our neglect of doubly excited resonances in the calculations. This possibility points to the importance of an accurate theoretical description of doubly excited states of open-shell atoms. The similarity of the Cl and Br spectra in this energy range is not as pronounced as their similarity near the ${\mathit{ns}}^2$ ${\mathit{np}}^4$ thresholds.