RESONANCE ENHANCEMENT OF ELECTRON-IMPACT EXCITATION RATES FOR ARGONLIKE IONS

We have calculated the electron-impact excitation-rate coefficients for the 3p-3d transitions of Ar-like ions with Z = 42, 54, and 63. The direct-excitation rates were evaluated with relativistic multiconfiguration target wave functions in a distorted-wave approximation. The contributions from the autoionizing resonances were calculated by the multiconfiguration Dirac-Fock method. For most transitions, autoionizing resonances are found to enhance the rate coefficients by factors of 2-3 for electron temperatures below the temperature at which peak excitation occurs. The enhancement is much less at higher temperatures.