Refraction effects in angle-resolved photoemission from surface states on metals

Effects of refraction of $p$-polarized light are shown to be of importance in understanding angle-resolved photoemission data from surface states on metals as a function of the photon energy. Special attention is paid to photon energies near the bulk-plasmon energy of the metal, and it is shown that refraction effects are responsible for the observed suppression of normal photoemission from surface states in this energy range. Theoretical calculations of the cross section for normal photoemission are presented for a simplified "local" dielectric model of a tungsten surface, which exhibit simple forms of the electronic wave functions in the initial and final states and which incorporate refraction effects. The model is evaluated critically, and an effort is made to isolate results considered to be of general validity.