Angular distribution of ejected electrons in resonant Auger processes of Ar, Kr, and Xe.

Abstract

Angle-resolved electron spectroscopy with the help of synchrotron radiation has been used to study resonant Auger processes near the core shells of Ar 2p, Kr 3d, and Xe 4d. Results for the lowest-energy resonances have received special attention: argon (Ar 2${p}_{3/2}$\ensuremath{\rightarrow}4s) at a photon energy of 244.4 eV, krypton (Kr 3${d}_{5/2}$\ensuremath{\rightarrow}5p) at 91.2 eV, and xenon (Xe 4${d}_{5/2}$\ensuremath{\rightarrow}6p) at 65.1 eV. The angular distribution parameters \ensuremath{\beta} are evaluated for each of the resolved Auger peaks. Most striking is the occurrence of large negative \ensuremath{\beta} values for some of the higher kinetic energy peaks. The results are most apparent under high electron resolution. The theoretical basis for having \ensuremath{\beta} values near -1 is discussed. In particular, the experimental results for argon are found to be in general agreement with the prediction of -1 \ensuremath{\beta} values by using either angular momentum transfer theory or normal Auger theory. However, a better understanding of the range of \ensuremath{\beta} values will have to await explicit calculations. Experimental results on the Auger spectra are also given at lower kinetic energies, for shakeup states, and for higher-energy resonances, especially those involving vacancies in the core shells of the lower spin states. It is shown that, although transitions having the same final state of the singly charged ion frequently have similar relative intensities and \ensuremath{\beta} values, occasionally they differ quite markedly. The theoretical consequences of variant behavior for processes having the same final states are also discussed.