PHOTOELECTRON ANGULAR-DISTRIBUTIONS FOR THE OUTER SHELL OF THE ALKALI-METAL ATOMS

Dirac-Fock calculations of the photoionization of the outer ns electrons in Na, K, Rb, and Cs have been performed. The resulting photoelectron angular distribution asymmetry parameters β show strong variations with energy, in contrast to the nonrelativistic prediction of β=2, independent of energy, for s electrons. This deviation is due to the spin-orbit interaction of the continuum electron which gives rise to two final states εp12 and εp32, in place of the single εp nonrelativistically. The transitions to the εp12 and εp32 have matrix elements and phase shifts which differ and interfere, thereby resulting in an energy-dependent β. The effects are particularly dramatic between the Cooper minima in the two channels, and they persist even for Z as low as that for Na. © 1979 The American Physical Society.