Vacancy multiplication following NiL-shell photoionization

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 created in all three L subshells, in the $L_2$,3 subshells, and in the $L_3$ subshell alone, and the resultant $L_3$-$M_4$,5${\mathrm{M}}_4$,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. Four channels leading to the four–3d-hole final state and three channels leading to the three-hole state, including Auger cascades and shake processes, were clearly identified and their respective roles established, convincingly verifying a model proposed by Mårtensson et al.