Site-dependent fine structure in photoemission branching ratios

The photoemission intensity ratio between the 4d3/2 and 4d5/2 spin-orbit-split states of the Sb 4d core level, known as the branching ratio, shows fine-structure oscillations as a function of photon energy, which are different for the Sb /Si(111)- (3×3) and (53×53) adsorbate structures. We demonstrate that this branching ratio fine structure is related to the diffraction χ function, and can be used to deduce the adsorbate atomic structure. The dependence of the branching ratio on atomic bonding geometry has important implications for high-resolution core-level line shape analyses.