Relativistic Effects on Low-Energy5s→εpPhotoionization for Xenon

Under suitable conditions, relativistic corrections to the interaction of a photoelectron with its parent ion are enhanced, giving rise to large anisotropic final-state effects which can be observed in the photoelectron angular distribution. The particular example of $5s\to \epsilon p$ photoionization of Xe is considered in detail. It is shown that the angular asymmetry parameter $\beta$ is reduced by a factor of 9 from its nonrelativistic value of 2 near the $5s$ "Cooper minimum," so that the energy dependence of $\beta$ becomes a sensitive test of atomic correlation theories.