Relativistic photoelectron angular distribution parameters in the quadrupole approximation

Relativistic calculations of the parameters beta, gamma and delta of the ph otoelectron angular distribution have been carried out using the quadrupole approximation for a number of atoms at photoelectron energies up to 10000 eV. The calculations have been performed using the Dirac-Fock (DF) atomic m odel, the exchange interaction having been taken into account exactly for t he interaction both between bound electrons and between bound and free elec trons. The influence of approximations in the exchange treatment on the mag nitude of the parameters is shown to be essential at small photoelectron en ergies and in the energy regions where parameters become small, changing si gn. The comparison between the above relativistic and our nonrelativistic H artree-Fock calculations is made. Peculiarities of the parameters' behaviou r are discussed. The DF calculations of the combined nondipolar parameter g amma + 3 delta for the 2p shell of Kr are in good agreement with available experimental data.