Site-Dependent Fine Structure in Photoemission Branching Ratios

The photoemission intensity ratio between the 4{ital d}{sub 3/2} and 4{ital d}{sub 5/2} spin-orbit-split states of the Sb 4{ital d} 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)-({radical}3{times}{radical}3) and (5{radical}3{times}5{radical}3) adsorbate structures. We demonstrate that this branching ratio fine structure is related to the diffraction {chi} 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.