Nondipole parameters in angular distributions of electrons in photoionization of noble-gas atoms

The parameters that determine the nondipole $(E1\ensuremath{-}E2)$ corrections to the photoelectron angular distribution have been investigated for the $s\ensuremath{-}$ and p-subshells of the noble-gas atoms through comparing results calculated in the Hartree-Fock (HF) approximation and taking into account multielectron correlations, using the random-phase approximation with exchange. Our results cover the photoelectron energy range $\ensuremath{\epsilon}$ from the photoionization thresholds to 1.6 keV. We find the interesting result that near the photoionization thresholds these parameters are generally characterized by an oscillatory behavior as a function of $\ensuremath{\epsilon},$ exclusive of the parameter for the He $1s$ subshell. These oscillations are sensitive to multielectron correlations, except those of the Ar $3p$ subshell. This finding supports once more that the photoprocesses in these atomic subshells are of a collective character. We conclude that their correct description cannot be achieved within the framework of a one-electron approximation such as the HF approximation. Results are presented and discussed.

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