New experimental technique of photoelectron holography applied to Bi trimers on Si(111)

The branching ratio, the photoemission intensity ratio of two spin-orbit-split components, has been applied for the first time as a means for obtaining a photoelectron holographic image. Angle-resolved photoemission from a monolayer of Bi adsorbed on Si(111) shows fine-structure oscillations in the branching ratio of the Bi 5d core level due to diffraction effects. These oscillations as a function of photon energy are recorded for a number of emission angles. Three-dimensional holographic inversion of the data yields an atomic image which shows that the Bi adatoms are arranged in a trimer structure.