High resolution study of the inner-shell 3p-3d and 3p-5s resonance regions in calcium atoms

The 3p⁵4s²3d 1P1 and 3p⁵( ²P₃/₂)4s²5s ²[3/2]1 resonance regions of Ca atoms have been studied experimentally with the aid of synchrotron radiation excited electron spectroscopy. The strong configuration interaction of the 3p⁵4s²3d, 3p⁵4s ²5s and several other nearly degenerate configurations leads to complex structures observed in the photoelectron yield spectrum. Multiconfiguration Dirac-Fock (MCDF) calculations have been performed for these 3p-excited resonances of neutral calcium and compared to experimental results. The excitation and subsequent autoionization of these resonances lead to the final ionic 3p⁶nl states from which new high-lying members of the Rydbergp-series have been resolved experimentally. These new levels agree reasonably well with calculations as well as with the extrapolation of the Rydberg formula. The post collision interaction (PCI) effect has been observed in the transition Ca⁺ 3p⁵3d4s ²P1/2,3/2 Ca ²⁺ 3p^{6 1}S₀ + eT_er and explained by means of the rather long core-hole lifetime, while the decay of Ca⁺ 3p⁵3d4s ⁴P1/2,3/2,5/2 states is not affected by PCI.