SITE-DEPENDENT FINE-STRUCTURE IN PHOTOEMISSION BRANCHING RATIOS

The photoemission intensity ratio between the 4d(3/2) and 4d(5/2) spin -orbit-split states of the Sb 4d core level, known as the branching ra tio, shows fine-structure oscillations as a function of photon energy, which are different for the Sb/Si(111)-(root 3 X root 3) and (5 root 3 X 5 root 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 o f the branching ratio on atomic bonding geometry has important implica tions for high-resolution core-level line shape analyses.