DIELECTRONIC RECOMBINATION OF NI-LIKE, CU-LIKE, 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-, an Ar-like tu ngsten in the ground state were performed. Similar calculations were c arried out for Ni-like barium for comparison. The most important low-l ying inner-shell excited configuration complexes are taken into accoun t, namely (3p3d)(15)4141' for Ni-like W and Ba, (3p3d)(15)4s4141' for Cu-like W, and finally 3p(5)3d91; 3s3p(6)3d71, and 3p(5)4141' for Ar-l ike 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 mix ing is taken into account when significant. The energy levels of the t ungsten 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 coeff icients for Cu-like tungsten are found to be very close in magnitude t o those of the Ni-like ion. Some partial contributions to the DR rate coefficients are found to rise dramatically at very low electron tempe rature, a fact that has been observed experimentally for lighter ions. It is found that high-1 3p(5)3d91 configurations, that were previousl y neglected, may have a significant contribution to the DR of Ar-like tungsten. The effect of electron collisions with the inner-shell excit ed ions is shown to influence the DR rate coefficient only at very hig h electron densities, greater than 10(20) cm(-3) for Ni-like W and gre ater than 10(22) cm(-3) for Ar-like W. In the Ni-like case at an elect ron density of 10(23) cm(-3) these collisions enhance the DR rate by a bout 30% at 5 keV, and by as much as a factor of 2 at 200 eV. (C) 1997 Elsevier Science Ltd. All rights reserved.