Optical-potential treatment of inelastic effects and its implications for band mapping are discussed. Interference effects arising form the coherent nature of the final state in the one-step theory are shown to strongly affect the frequency dispersion of photoemission peaks. Thus, information on just dispersion of initial and final states is often insufficient to understand the experimental results.
Applications to valence band photoemission from VSe2 and TiTe2 layered crystals and to emission form the surface states on Al(100), Al(111), and Cu(111) surfaces are presented. Theoretical and experimental study of VSe2 and TiTe2 provides evidence of a multi-Bloch-wave structure of the photoelectron final states. Constructive interference that accompanies direct transitions to the composite final states leads to experimentally observed structures with characteristic frequency dispersion. The effects of the photoelectron lifetime on the line shape is discussed, and it is shown how the electron hole lifetime can be determined from the photoemission experiment.
The study of the surface state photoemission covers the final state kinetic energy range up to 100 eV and reveals strong multiple-scattering (band structure) effects at high energies. The elastic scattering origin of the emission windows and the role of complex band structure in formation of the spectra is discussed [2].
[1] E.E. Krasovskii, Phys. Rev. B 70, 245322 (2004).
[2] E.E. Krasovskii, W. Schattke, Phys. Rev. Lett. 93, 27601 (2004).