Anisotropy of the spin-orbit branching ratio in angle-resolved photoemission from adsorbate layers

Abstract The angular variation of the spin-orbit branching ratio of In 4d photoemission doublets from ordered In overlayers on the Si(001) surface was investigated. The branching ratios show strong angular anisotropy in the investigated photon energy range of 70–100 eV, which depends both on the surface structure and the photon energy. It is demonstrated that the anisotropy in this energy range is caused by an inherent difference in the photoelectron waves of the 4 d 5 2 and 4 d 3 2 levels via photoelectron diffraction.