EXCITATION-AUTOIONIZATION CROSS-SECTIONS AND RATE COEFFICIENTS OF ZN-LIKE IONS

Detailed level-by-level calculations of the excitation-autoionization (EA) cross sections and rate coefficients were performed using the rel ativistic distorted-wave method along the Zn isoelectronic sequence fo r all the elements with 34 less than or equal to 2 less than or equal to 92. While in a previous work only the 3d-4l inner-shell collisional excitations were taken into account, the present calculations also in clude excitations to higher configurations: 3d(9)4s(2)nl (n = 4 to 7) and 3p(5)3d(10)4s(2)nl (n = 4,5). An extrapolation method is used to e valuate the total contribution for the higher principal quantum number s. Configuration mixing and secondary autoionization processes followi ng radiative decay from autoionizing levels are also included. The res ults show that the total EA rate is dominant compared to the direct io nization rate, up to a factor 12 at Z=47. The additional inner-shell e xcitations for Z<59 produce an increase in the EA effect varying from 25% to almost a factor of 2, with respect to the previously predicted EA effect through 3d-4l only. The excitations to the higher configurat ions are the most significant for heavy elements with Z greater than o r equal to 61, since they open EA channels, resulting in an EA rate wh ich varies along the sequence from 4 to 1 times the direct-ionization rate.