Photoelectric Studies of Iron

Studies of the photoelectric properties of spectroscopically pure, carefully outgassed iron were made through a wide temperature range, including the $\alpha \to \beta$ and $\beta \to \gamma$ transformation points. Interesting changes in the slope of the temperature-photoelectric current curves for the various monochromatic radiations are shown. Analyses of the data by Fowler's method at different temperatures indicate that the change in photoelectric sensitivity, to be associated with the allotropic states of iron, is explainable more on a change in the number density of free electrons and the transition-probability factor than on a change in the surface work function. The work function of iron at room temperature was found to be 4.70 electron-volts. The variation of the work function for the three allotropic forms $\alpha$, $\beta$, and $\gamma$ is only 0.10 electron-volt.