The Determination of the Photoelectric Threshold for Tungsten by Fowler's Method

Abstract

The photocurrent per unit intensity curves for two different tungsten surfaces have been replotted by means of the method suggested by R. H. Fowler. The points all fit the theoretical curve very well, although the thresholds for the two surfaces are different. For one surface the data were obtained at temperatures of 1100, 900 and 790\ifmmode^\circ\else\textdegree\fi{}K. The average value of the threshold at 0\ifmmode^\circ\else\textdegree\fi{}K was 2632A, or 4.69 volts, with a greatest difference between individual values of 1.3 percent. The thermionic work function of this surface was 4.71 volts. The second surface was investigated at room temperature, and was formed by evaporation after very careful outgassing. The threshold for this surface was 2720A or 4.54 volts at 0\ifmmode^\circ\else\textdegree\fi{}K, which agrees with Dushman's value of 4.54 volts for the thermionic work function at the same temperature. This should be regarded as the most reliable value.