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.
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