Photoelectric emission from a W or W-Ba tip subjected to an electric field

The photoelectric emission from a pure or barium-coated single crystal tungsten tip submitted to a high electric field is studied under illumination by light of energy smaller than the work function of the substrate. The results are discussed according to the range of the electric field applied. It is found that the average values of the work function for barium coated tips as obtained by photofield emission are different from those obtained by field emission. The photofield emission and field emission patterns are compared. (Auth.)