The Photo-Electric Method for the Determination of h/e

The experimental foundations of the photoelectric method for the determination of h/e have been re-examined. The theory of the normal energy distribution of photoelectrons has been modified by including the effect of contact potentials; it is shown that the stopping potential at 0° K. should be independent of variations of the cathode work function. Apparatus has been constructed for the precise determination of the normal energy distribution of photoelectrons from sodium. Photoelectric currents emitted by monochromatic light were accurately measured after passage through a retarding field. The results of such measurements are found to vary with changes of the anode potential barrier. Energy distribution curves taken at different frequencies exhibit very satisfactory mutual consistency; when plotted logarithmically they are of identical shape. This shape does not agree with the theoretically predicted normal energy distribution. The reasons for this discrepancy are discussed, and an explanation is given in terms of the structure of the anode potential barrier. A method for the determination of h/e based on the consistency in shape of the empirically determined curves has been developed, and preliminary results have been obtained. The errors of the method are discussed, and modifications for its further improvement are suggested.