Photofield Emission Spectroscopy of Ba on W

Optical transitions in photofield emission from barium covered tungsten were observed. The initial energies of the excited electrons obtained for different crystallographic planes range near the values of s₁ = -0.07 ± 0.02 eV and s₂ = -0.28 ± 0.04 eV with respect to the Fermi level. The energies are ascribed to electrons in the thin barium layer. The work functions of the barium covered tungsten (100), (111) and (100) planes were estimated using field emission method. In order to measure very small photocurrents a modulated laser radiation and the phase-sensitive detection were used.