The Emission and Absorption of Photoelectrons by Platinum and Silver

A S the result of light passing through very thin metal foil, photoelec-^~* trons will be emitted from both sides of the metal simultaneously.Since it will be necessary to distinguish between those electrons which are liberated from the side upon which the light is incident and those that come from the side from which the light emerges, we shall refer to them as "incidence" and "emergence" rays respectively.It was hoped that some relations could be established between the atomic properties of metals and their photoelectric emissivity.Secondly to establish the magnitude of the coefficient of absorption of the electrons as a function of their speed and atomic properties of the metal in which the absorption was to take place.Finally to use the above information, if adequate, to throw some light on the structure of the atom.All previous work by the writer and other investigators 2 who have been interested in the photoelectric properties of very thin metallic foil, or still thinner and transparent films of metal was undertaken with cathode deposited films supported by quartz.The photoelectric currents and velocity investigations were, however, found to depend too much upon the previous history of the cathode and the potential gradient under w^hich the cathodic deposit had been made to warrant any quantitative conclusions.Thus in many cases, as in those investigations by the writer and K. T. Compton, both the magnitude of the current and the velocity of emission of the electrons could be altered at will, depending upon the impurities that are present through occlusion, in the cathode.The most serious difficulty, however, was found in mounting the very thin transparent films in such a way as to insure perfect electrical contact.These sources of error were so great that no quantitative conclusions could be drawn from the data at that time.