Momentum-dependent energy losses in core level photoemission spectra of poorly conducting metals -: art. no. 197602

Angular resolved photoemission spectra of 5d core levels from Bi(111) exhibit a component which is split off in energy by approximate to200 meV. The energy as well as the spectral width and relative intensity of the split off structure are strongly modulated by the final state electron momentum k(perpendicular to) and k(parallel toparallel to), resembling the periodicity of the surface and bulk Brillouin zone. The data can be explained by a k-dependent energy loss function Im[-1/epsilon(k)(omega)] composed of indirect and direct interband transitions from various parts of the bulk Brillouin zone.