Dramatic effects of relaxation on many-body interactions: Theoretical and experimental study of atomic photoionization of outer shells in the vicinity of inner-shell thresholds

Experimental studies of the Xe 4d5/2:4d3/2 branching ratio in the vicinity of the inner shell 3d thresholds have been made and exhibit significant structure owing to interchannel coupling. New calculations at the Relativistic-Random-Phase Approximation (RRPA) also are reported here in which core relaxation has been included (RRPA-R) and this brings theory and experiment into excellent agreement. Earlier RRPA calculations that ignore relaxation are in both quantitative and qualitative disagreement with the present experimental results.