Dielectronic recombination rate coefficients of Ni-like barium and tungsten

Ab initio calculations of the total dielectronic recombination (DR) rate coefficient of Ni-like barium () and tungsten () in the ground state have been performed using the HULLAC atomic code package. Resonant and nonresonant stabilizing radiative transitions are included. Collisional transitions following electron capture are neglected. The present level-by-level calculations include the DR contributions of all of the levels (over 17000) in the Cu-like inner-shell excited configurations 3d ⁹ 4ln'l' (), 3p ⁵ 3d ¹⁰ 4ln'l' (), and 3s3p ⁶ 3d ¹⁰ 4ln'l' (). For both ions, the configuration complexes with a hole in the 3p inner shell contribute almost 10% to the total DR rate coefficient, while the complexes with a hole in the 3s inner shell contribute about 1%. The converging contributions of the 3d ⁹ 4ln'l' (n' > 9) configurations are evaluated by applying the complex-by-complex extrapolation method and are found to comprise up to about 20% of the total DR rate coefficients throughout a wide electron temperature range. The total DR rate coefficients are fitted to an easy-to-use analytic expression which reproduces the original data with an accuracy of about 2% or better in a very wide temperature range. Received: 1 February 1999