No abstract

No abstract

No abstract

The authors consider an analytic model of the screened potential of a neutral atom based on a generalised Hulthen potential. The model is characterised by its high degree of solvability and gives expressions for the screened-Coulomb normalisation factors and phaseshifts which are relatively simple and are also in good agreement with the results of the exact numerical calculations. The formulae for normalisation factors and phaseshifts are further investigated in the limit of weak screening. Another method which can be used to deal directly with the limit of this type is the analytic perturbation theory (APT) for screened-Coulomb potentials, based on an expansion of the screened atomic potential at small distances.

No abstract

We study spin and polarization correlations in atomic photoionization from np J subshells, including the first retardation corrections to the dipole approximation. This extends previous work on distributions of unpolarized photoelectrons ejected by polarized photons [A. Bechler and R. H. Pratt, Phys. Rev. A39, 1774 (1989), A42, 6400 (1990)]. A non-relativistic Pauli-Schrödinger approach in a self-consistent central potential is used, neglecting spin-orbit coupling. There are nontrivial correlations, even in this non-relativistic approximation, 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 polarisation correlations in the non relativistic approach.). Explicit formulas 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.

No abstract

No abstract