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Photo-Electric Thresholds and Fatigue
Phys. Rev. 32, 657 – Published 1 October, 1928
DOI: https://doi.org/10.1103/PhysRev.32.657
Abstract
Photo-electric fatigue.—Using elements of the highest purity, clean surfaces were prepared, in a vacuum of the order of mm of Hg, by means of an electromagnetic filing device. A linear relation was found between the logarithm of the photo-electric current and the logarithm of the time elapsed since polishing the specimen. The rate of fatigue depends upon the element used and the factors which produce fatigue and, for a given substance, increases numerically as the threshold is approached. Increasing the pressure increases the rate of fatigue. The action of light has a negligible effect.
Photo-electric thresholds.—The values for Ca, Fe, Co, Ni, Cu, Zn, and Ge are, respectively, 4475, 3155, 3165, 3040, 2955, 3180, and 2880A. Within a period of several hours at least photo-electric fatigue causes no change in these values when a high vacuum is used. Evidence for a shift towards shorter wave-lengths is obtained for lower vacua.
The "patch" theory.—A theory in which contamination takes place at discrete areas of the surface of the element is proposed to account for the experimental facts obtained.
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