Dielectronic recombination of Co-like gold ions

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: 3d(3/2)(3)3d(5/2)(6) n'l', 3p(5) 3d(10) n'l',3s 3p(6) 3d(10) n'l', 3d(8) 4ln'l', 3p(5) 3d(9) 4ln'l' and 3s 3p(6) 3d(9) 4ln'l' with n' <= 25, and 3d(8) 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 3d(8) 4ln'l' and 3p(5) 3d(9) 4ln'l'. The complex series 3p(5) 3d(10)n'l' and 3d(8) 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 nonresonant 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 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 Colike gold. In addition, some comments on the published DR data for the NiI isoelectronic sequence are drawn from the present calculation.