Higher multipole and retardation effects in the spin and polarization correlations of polarized photoelectrons ejected from the 2p_<i>J</i>subshell by polarized photons - a nonrelativistic approach

We study spin and polarization correlations in atomic photoionization from npJ subshells, including the first retardation corrections to the dipole approximation. This extends previous work on distributions of unpolarized photoelectrons ejected by polarized photons (Bechler A and Pratt R H 1989 Phys. Rev. A 39 1774, 1990 Phys. Rev. A 42 6400). A nonrelativistic Pauli-Schrödinger approach in a self-consistent central potential is used, neglecting spin-orbit coupling. There are nontrivial correlations, even in this nonrelativistic approximation, and even without taking into account spin-orbit coupling, provided the electron is ejected from a subshell with a definite value J of the total angular momentum. (However, if summation over J is performed, one would have to include the spin-orbit coupling in order to obtain any remaining spin and polarization correlations in the nonrelativistic approach). Explicit formulae are given in terms of dipole and quadrupole radial matrix elements and phase shift differences. Results are compared with exact numerical calculations. Corrections to the dipole approximation are generally small at low energies and low Z, but increase with energy and atomic number. Including the first retardation corrections significantly improves agreement.

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