The theory of the angularly dependent photoemission from a semi-infinite crystal as a one-step process is briefly reviewed, starting from the formulas of Adawi and using surface-matched wave functions in both upper and lower states and absorption in the upper state. We derive conditions under which the three-step model can be justified. The angle-resolved photoemission from Ag(111) is calculated from the three-step formula with transmission factors and matrix elements obtained from a self-consistent potential for Ag, and compared with experimental data of Gustafsson et al. The transmission factor has a small effect, amounting to a nearly constant factor of 0.55 at all angles over the energies of interest; the dependence on the angle of incidence of the radiation is much stronger and is in agreement with observation.

• Received 17 February 1976

DOI:https://doi.org/10.1103/PhysRevB.15.1728