Calculations of photoionization with excitation for Ca using theR-matrix approach

Calculations of photoionization accompanied by excitation are reported for Ca using the R-matrix approach. Cross sections for leaving the ${\mathrm{Ca}}^{+}$ ion in the states 3$p^6$4s, 3$p^6$3d, and 3$p^6$4p are presented from the 4p threshold to a photon energy of 26 eV. Extensive configuration-interaction wave functions are used to describe both the initial and final states, and coupling between continua based on different thresholds is also included. The results differ considerably from previous calculations where coupling between the continua has been neglected. We show that in particular the 4$s^2$→4sεp cross section is very sensitive to a number of factors. It is predicted that the 3d photoelectron satellite will be stronger than the main line (4s) from below the 4p threshold up to approximately 12 eV. No experimental measurements exist at the moment below 21.22 eV. At this energy there is reasonable agreement between the different calculations and with experiment.