Outstanding spin-orbit-activated interchannel coupling in the Cs and Ba 3d photoemission

Abstract

Partial 3d(5/2) photoionization cross sections of atomic Cs and Ba as well as the asymmetry parameter beta of the angular distribution of the Cs 3d(5/2) photoelectrons were investigated near the threshold of the 3d(3/2) channel at about 750 eV and 800 eV, respectively. Strong electron correlations, in particular, the spin-orbit activated interchannel coupling between the 3d(5/2) and 3d(3/2) channels, govern the observed spectra. The most striking effect was found for beta(5/2) of Cs with a dramatic increase from beta=1.0 to beta=1.5 in the energy region where the mixing between both channels causes a pronounced minimum in the partial 3d(5/2) cross section. This result indicates the decisive influence of the interference term on the asymmetry parameter beta with its dependence on the phase difference between the outgoing p and f waves.