Spin-orbit-activated interchannel coupling in the 3d photoionization of barium atoms

We have measured the NEXAFS spectrum and the relative photoionization cross section of the 3d spin - orbit components of the barium atom in the energy range up to 50 eV above the ionization threshold. As in Xe and Cs, also in barium the two spin - orbit components show strongly different energy dependence. A strong enhancement of the 3d(5/2) cross section near the 3d(3/2) ionization threshold, which is attributed to interchannel coupling, is observed. The experimental results are in good agreement with the relativistic time- dependent density functional theory calculations.