A new analysis of X-ray adsorption branching ratios: Use of Russell–Saunders coupling

The intensities of X-ray absorption peaks at core-level edges are considered in terms of Russell–Saunders multiplets. The contributions of different multiplets to the relativistic wavefunctions of the excited states are determined and the absorption intensity related to the contributions of the dipole allowed multiplets. This is a powerful method because the selection rules for multiplets are stronger than for relativistic J levels. It is also shown that differences in the radial extent of the spin–orbit split core spinors modify the intensity given by these symmetry arguments. Applications are considered for cases involving different degrees of Russell–Saunders or j–j coupling.