Nielsen, J. Rud (1925) On the Influence of Temperature upon the Photo-electric Effect. Physical Review, 25 (1). pp. 30-40. ISSN 0031-899X http://resolver.caltech.edu/CaltechAUTHORS:NIEpr25
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Photo-electric threshold frequency for metals.—Free electron theory. A discussion is given of the suggestion by Millikan that in the photo-electric effect the energy of the light is transferred to the free electrons of the metals as well as to the bound electrons, and the threshold frequency ν0 is interpreted by the equation hν0=ϕp-Ek where ϕp is the work necessary to remove a free electron from the metal. In cases where Ek is not small compared with ϕp the theory leads to a lack of sharpness in the definition of ν0. Neglecting variations of kinetic energy, the difference of stopping potentials comes out equal to the Peltier coefficient; hence the uniformity of stopping potentials for different metals observed by Millikan is due, according to the theory, to the smallness of the Peltier effect. The variation of the long wave-length limit with temperature comes out ∂λ0/∂T=(λ02/hc)eσ, σ being the Thomson coefficient. In most cases λ0 should be practically independent of temperature. In the case of aluminum, after prolonged heating, the photo-electric current due to λ2537 was found to remain constant within 1/2 per cent as the target was cooled from 400° to 100°C and this constancy is interpreted as evidence that the shift of the long wavelength limit with change of temperature is less than 1A. The limit was found to be at about 2700A. Similar observations with a nickel target and 2412A gave inconclusive results, as in spite of heating to 1300°C and reduction of the oxide on the surface by heating in hydrogen, reproducible results were not obtained. Photo-electric current from aluminum for λ2537.—(1) Effect of prolonged heating in vacuum by high frequency induction for many hours to near the melting point. The current remained strong. (2) Effect of cooling from 400° to 100°C. The current remained constant within 1/2 per cent.
|Additional Information:||©1925 The American Physical Society Submitted December 1923. Received May 16, 1924. In conclusion, the author wishes to express his great indebtedness to Professor R. A. Millikan who suggested the problem and under whose direction this work was done. [J.R.N. was a] Fellow of the American-Scandinavian Foundation, 1922-23.|
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