Excitation-autoionization cross sections and rate coefficients of Cu-like ions.

Abstract

Detailed level-by-level calculations of the excitation-autoionization (EA) cross sections and rate coefficients were performed using the relativistic distorted-wave method along the Cu isoelectronic sequence for all the elements with 34\ensuremath{\le}Z\ensuremath{\le}92. While in a previous work only the 3d-4l inner-shell collisional excitations had been taken into account, the present extensive calculations include the 3${\mathit{d}}^{10}$4s-3${\mathit{d}}^{9}$4snl (n=4--7 and l=0--n-1) and the 3${\mathit{p}}^{6}$3${\mathit{d}}^{10}$4s-3${\mathit{p}}^{5}$3${\mathit{d}}^{10}$4snl (n=4,5 and l=0--n-1) excitations. An extrapolation method is used to evaluate the contribution for higher principal quantum numbers. Configuration mixing and secondary autoionization processes following radiative decay from autoionizing levels are also included. The results show that the EA processes give a dominant contribution compared to direct ionization, up to a factor of about 15 at Z=43. The additional inner-shell excitations for Z55 produce an increase in the EA effect varying from 20% to a factor of 2, with respect to the previously predicted 3d-4l EA rates. The additional excitations are the most significant for heavy elements with Z\ensuremath{\gtrsim}55, since they open EA channels, resulting in an EA rate varying typically along the sequence from 3 to 1 times the direct ionization rate. \textcopyright{} 1996 The American Physical Society.