Dielectronic recombination of Co-like gold ions

Abstract

Ab initio calculation of the total dielectronic recombination (DR) rate coefficient from the ground and the first excited states of Co-like gold is performed employing the relativistic distorted-wave approximation with configuration interaction. The DR contributions are explicitly taken into account from the relevant complexes of a Ni-like ion: 3d33/2 3d65/2n′l′, 3p5 3d10n′l′, 3s 3p63d10n′l′, 3d8 4ln′l′, 3p5 3d9 4ln′l′ and 3s 3p6 3d9 4ln′l′ with n′ ⩽ 25, and 3d8 5ln′l′ with n′ ⩽ 9. The contributions from a higher n′ complex are evaluated by an extrapolation procedure. The DR contributions mainly come from complex series 3d8 4ln′l′ and 3p5 3d9 4ln′l′. The complex series 3p5 3d10n′l′ and 3d8 5ln′l′ also contribute significantly to the total DR rates at low and high electron temperatures, respectively. The l′ and n′ dependences of the partial rate coefficient are investigated. The possible important decays into autoionizing levels followed by radiative cascade (DAC) from the resonant levels are taken into account, as well as the resonant stabilizing and non-resonant stabilizing transitions. The inclusion of DAC transitions enlarges the total DR rate coefficients by a factor of about 10% and may break down the usual n′−3 scaling law of the partial DR rates along some complex series. To evaluate the high n′ contributions from these complex series, the level-by-level extrapolation method is developed to include DAC effects. The total DR rate coefficients are fitted to an empirical formula. The present results are compared with those from the semiempirical Burgess–Merts approximation. The DR rate coefficients of Ni-like gold are also presented and compared to those of Co-like gold. In addition, some comments on the published DR data for the NiI isoelectronic sequence are drawn from the present calculation.