Dielectronic recombination of Rh-like Gd and W

Ab initio calculations of dielectronic recombination rate coefficients of Rh-like gadolinium and tungsten have been performed. Energy levels, radiative transition probabilities, and autoionization rates of Pd-like gadolinium and tungsten for [Zn]4${p}^{6}$4${d}^{8}$4fnl, [Zn]4${p}^{6}$4${d}^{8}$5${l}^{\ensuremath{'}}$$nl$, [Zn]4${p}^{6}$4${d}^{8}$6${l}^{\ensuremath{'}}$$nl$ and [Zn]4${p}^{5}$4${d}^{10}nl,$ [Zn]4${p}^{5}$4${d}^{9}$4fnl, [Zn]4${p}^{5}$4${d}^{9}$5${l}^{\ensuremath{'}}$$nl$, [Zn]4${p}^{5}$4${d}^{9}$6${l}^{\ensuremath{'}}$$nl$ ($n$ \ensuremath{\leqslant} 18) complexes were calculated using the flexible atomic code. The contributions from resonant and nonresonant radiative stabilizing transitions to the total rate coefficients are discussed. Results show that the contributions from nonresonant radiative stabilizing transitions are significantly enchanced for W when compared with Gd as a result of lowering of energy levels relative to the ionization limit. In addition, the widely used Burgess-Merts semiempirical formula may underestimate the dielectronic recombination rate coefficients in the temperature regions of interest. The present calculated rate coefficients are fitted to a semiemperical formula. The data obtained are expected to be useful for modelling plasmas both for extreme ultraviolet lithography source development and for fusion applications.