Study of parameters of the angular distribution of photoelectrons in the relativistic quadrupole approximation

Relativistic calculations of differential cross sections for photoionizatio n are performed and the behavior of parameters beta, gamma, and delta descr ibing the angular distribution of photoelectrons in the quadrupole approxim ation is studied. The calculations were carried out for a number of atoms f or kinetic energies of photoelectrons E-k less than or equal to 50 000 eV. The electronic wave functions of the initial and final states are calculate d by the Dirac-Fock method taking into account the exchange interaction and a hole produced in the atomic shell upon photoionization. The dependence o f parameters beta, gamma, and delta on the physical assumptions used in the calculations is studied. Comparison with nonrelativistic calculations show s that relativistic values of the nondipole parameters gamma and delta can be substantially different even at low energies of photoelectrons. Our calc ulations of nondipole parameters gamma and delta for the 2p-shell of the Kr atom better agree with the recent experimental data than nonrelativistic c alculations performed earlier taking approximately into account the exchang e interaction and neglecting a hole. (C) 2000 MAIK "Nauka/Interperiodica".