A study of the electric field dependence of subthreshold photoemission

Abstract

Experiments that detect electrons photoemitted from W(110) at energies below the vacuum level are reported. The data are obtained by performing energy resolved measurements of the electrons photoemitted from a tungsten field emission tip that is illuminated by focused UV lines from an argon–ion laser. Data on the final state energy distributions are analyzed by a theory that includes the transmission probability for an electron escaping from a metal–vacuum interface at energies below threshold. Data on the subthreshold photocurrent integrated over all final state energies reveal an oscillatory contribution when measured as a function of electric field. Fourier analysis of this data gives a frequency of (10.3±0.9)×104 (V/cm)1/2, a result that is in close agreement with previous measurements. The origin of this oscillatory structure has still not been conclusively established.