The shape of the total energy distribution from W(110) in sub-threshold photoemission

Measurements of the final state energy distribution of electrons photoemitted from W(110) at energies less than the vacuum level are presented. A 127° velocity selector analyzer was used to energy resolve the photoemitted current. A significant improvement in both energy resolution and signal-to-noise ratio over previous studies resulted. The energy distributions obtained from W(110) are compared the theoretical predictions based on a recent model of photofield emission. The sensitivity of this theoretical model to various parameters of interest are investigated. The reasonable agreement between theory and experiment indicates that the final states probed in these measurements are free electron-like and not strongly representative of the final bulk density of states of the emitting material.