Direct and inverse surface photoemission: Sources of ambiguities near the fermi level

We show that the measured peak positions of direct- and inverse-photoemission features near the Fermi level are off from their true values by the order of the energy resolution. Sources of ambiguities are the energy and k resolution, asymmetric line shapes, and high backgrounds. Surface-state bands and/or surface emission which cross the Fermi level are particularly affected. As examples we discuss surface states on Ag(111) and Ge(111)−(2×1) as well as band-gap surface emission on Ni(110).