Dielectronic recombination of Ni-, Cu-, and Ar-like tungsten and barium through the low inner-shell excited configurations including collision processes

Level-by-level relativistic calculations of dielectronic recombination (DR) cross sections and rate coefficients for Ni-, Cu-, and Ar-like tungsten in the ground state were performed. Similar calculations were carried out for Ni-like barium for comparison. The most important low-lying inner-shell excited configuration complexes are taken into account, namely (3p3d)¹⁵4141′ for Ni-like W and Ba, (3p3d)¹⁵4s4141′ for Cu-like W, and finally 3p⁵3d91, 3s3p⁶3d71, and 3p⁵4141′ for Ar-like W. These complexes give the dominant contributions to the total DR rate coefficients for kT_e < 0.5 keV, and are still expected to give major contributions at higher electron temperature. Configuration mixing is taken into account when significant. The energy levels of the tungsten inner-shell excited DR channels are found to have typical j-j coupling characteristics, whereas those of Ni-like barium do not. The role of non-resonant radiative stabilizations is found to be generally minor for the Ni- and Cu-like ions. In contrast, for Ar-like tungsten these stabilizations are found to be very important. The DR rate coefficients for Cu-like tungsten are found to be very close in magnitude to those of the Ni-like ion. Some partial contributions to the DR rate coefficients are found to rise dramatically at very low electron temperature, a fact that has been observed experimentally for lighter ions. It is found that high-1 3p⁵3d91 configurations, that were previously neglected, may have a significant contribution to the DR of Ar-like tungsten. The effect of electron collisions with the inner-shell excited ions is shown to influence the DR rate coefficient only at very high electron densities, greater than 10²⁰ cm^-3 for Ni-like W and greater than 10²² cm^-3 for Ar-like W. In the Ni-like case at an electron density of 10²³ cm^-3 these collisions enhance the DR rate by about 30% at 5 keV, and by as much as a factor of 2 at 200 eV.