Regularities and irregularities in partial photoionization cross sections of He

We have combined B-spline basis sets with R-matrix theory for the description of photoionization in two-electron systems and applied this combination to the study of irregularities in He photoionization when doubly excited resonances up to the $N=9$ threshold of ${\mathrm{He}}^{+}$ are reached. Both total and partial photoionization cross sections have been obtained. Since the magnitude of the resonance effects is very similar for all partial cross sections, we believe that experimental investigations of photoionization cross sections leaving ${\mathrm{He}}^{+}$ in a highly excited state could provide the most information about possible long-range fluctuations in the photoionization cross sections.