Dynamics of Atomic Photoionization: Studies with Synchrotron Radiation.

The mechanisms that lead to states with three and four 3d vacancies following L-shell photoionization of metallic Ni have been investigated with synchrotron radiation. Vacancies were crated in all three L subshells, in the L_{2,3} subshells, and the L_3 subshell alone, and the resultant L_3-M_ {4,5}M_{4,5} Auger spectrum with its satellite structure was measured and analyzed. Auger diagram and satellite energies were computed in terms of a quasiatomic screening model, semiempirical shakeup and shakeoff cross sections were employed, and branching ratios were calculated from Auger transition theory with Hartree-Fock wave functions. In addition, the process which leads to the recapture of photoelectrons following near-threshold 2p photoionization of Ar has been investigated. The Russek-Mehlhorn semiclassical formalism of post-collision interaction was used to develop a theoretical model of the photoelectron recapture process. This model agrees well with the experimental data on Ar ion yields obtained with synchrotron radiation.