Doubly excited Rydberg states of He I and Ba I

The Auger decay widths of doubly-excited Rydberg states of He I and Ba I have been calculated by the multi-configuration Hartree-Fock procedure. The configuration mixing is crucial in obtaining the correct widths, while the energies seem to be relatively less sensitive to mixing. The usual mixing procedure is often unstable for doubly excited states and careful selection of configurations is required. An improved procedure for selecting the states for mixing is formulated, which seems to stabilize the calculation of both the energies and widths, with small numbers of configurations which are mixed. We apply the recipe to a selected set of doubly excited states of He and Ba. The long standing discrepancies in the widths for the series 7sns, 7snd, 8sns, and 8snd of Ba I with n > 11 may be explained by this procedure, except for the 7snd series. The calculated widths for the 7snd series are larger than the experimental values by a factor of 10-20. The difficulties of treating the states with both electrons in higher Rydberg orbitals are discussed.