Experimental and theoretical study of the Auger cascade following 2p → 4s photoexcitation in Ar

Resonant Auger transitions from the 2p(-1)4s photo-excited states in Ar to the 3p(-1)3s(-1)4s levels and the subsequent Auger decay to the 3p(4) states of Ar2+ are studied by means of angle-resolved electron spectroscopy. The branching ratios and the values of the angular anisotropy parameter beta are determined for the emitted electrons. The angular correlation between the two electrons emitted in the sequential transitions in the cascade are also measured in the coincidence experiment. All the experimental data are compared with MCDF calculations which include electron correlations in the initial, intermediate and final states of the cascade. It is found that although the electron energies are very well reproduced by the calculations, the calculated anisotropy parameters and angular correlation parameters for some of the transitions disagree with the experiment.