Relativistic multichannel calculation of the Ne KLL and Ar ${\mathit{L}}_2$${\mathit{M}}_{2,3}$${\mathit{M}}_{2,3}$ Auger transition rates

The multichannel multiconfiguration Dirac-Fock method has been used to study the Ne KLL and Ar ${\mathit{L}}_2$ ${\mathit{M}}_{2,3}$ ${\mathit{M}}_{2,3}$ Auger-electron transitions. Final-state correlation effects are accounted for by simultaneously including several ionic configurations and ionization channels in the calculation of the final-state many-electron wave functions. Our computational approach is based on scattering theory, which properly accounts for the incoming wave boundary condition. The line intensities from our test calculation for Ne KLL transitions are in good agreement with earlier theoretical results and with experiment. The interchannel coupling is stronger for the final states of the Ar ${\mathit{L}}_2$ ${\mathit{M}}_{2,3}$ ${\mathit{M}}_{2,3}$ transitions, but the net effect on the line intensities is somewhat smaller than that for Ne. Even the most extensive multichannel calculations are not fully able to reproduce the measured total rate and the ratio of ${}_{}{}^3{}_{}{}^{}$ ${\mathit{P}}_{0,1,2}$ to ${}_{}{}^1{}_{}{}^{}$ ${\mathit{D}}_2$ transition rates. The remaining discrepancy in the branching ratios of Auger lines is attributed to the omission of initial-state configuration interaction, whereas the discrepancy between the measured and calculated total rates is suggested to be mainly due to the neglect of relaxation. Our results indicate that, in analogy to outer-shell photoionization, the final-state interchannel interaction does not in general affect the strongest Auger lines very much when the kinetic energy of the Auger electrons exceeds about 200 eV.