Total dielectronic recombination rate coefficient for Co-like tungsten

Abstract

Ab initio calculation of the total dielectronic recombination (DR) rate coefficient from the ground state 3 s 23 p 63 d 9( J=5/2) of Co-like tungsten is performed employing the relativistic distorted-wave approximation with configuration-interaction. The DR contributions mainly come from complex series 3 d 84 ln′ l′. The complex series 3 p 53 d 10 n′ l′, 3 p 53 d 94 ln′ l′ and 3 d 85 ln′ l′ also contribute significantly to the total DR rates at relatively high electron temperatures. The l′ and n′ dependences of the partial rate coefficient are investigated. The inclusion of decays into autoionizing levels followed by radiative cascades (DAC) enlarges the total DR rate coefficients by a factor of about 10%. The level-by-level extrapolation method is developed to include DAC effects. The total DR rate coefficients are fitted to an empirical formula. It is shown that at temperatures above 2.5 keV the Burgess–Merts (BM) semiempirical formula can provide DR results with an accuracy of about 15%, whereas at electron temperatures below 100 eV it underestimates the DR rate coefficients by up to a few orders of magnitude and its temperature dependence is completely inadequate. The comparison of the results for Ni-like and Co-like tungsten shows that these two sets of DR rate coefficients are very close in magnitude at relatively high electron temperatures.