Photoionization cross sections with excitation to ${\mathrm{Ca}}^{+}$3d and 4p levels

Photoionization cross sections of neutral calcium with excitation to ${\mathrm{Ca}}^{+}$ 3d and 4p levels have been calculated from threshold to 50 eV by use of many-body perturbation theory. The cross section for leaving ${\mathrm{Ca}}^{+}$ in the 4s ground level is also presented in this energy range and compared with the 3d and 4p cross sections which at their thresholds are larger than the 4s cross section. All three cross sections show interesting structure near 31 eV due to the 3p→3d resonance.