Electron escape and photoemission in the threshold region.

Abstract

The formula giving the probability of electron escape is generalized to the case of electron excitation involving two conduction bands in the vicinity of the Brillouin-zone boundary when the gap between the bands is of critical importance. The escape probability in this case can be significantly larger than that found for excitation from the occupied states lying well within the first Brillouin zone. It is also shown that the Fowler law (commonly used to describe photoemission in the threshold region) is not restricted to the usually accepted assumption of indirect, momentum nonconserving, electron transitions but is a consequence of the linear dependence of the escape function on the electron energy near threshold and is valid for both direct and indirect electron transitions.