Photoelectric and Thermionic Properties of Palladium

Abstract

The photoelectric and thermionic properties of pure palladium were studied during an extended outgassing in high vacuum. The threshold, obtained by extrapolation of spectral sensitivity curves, shifted from below 2300A to above 3000A and then back to a final value of 2486A as outgassing progressed. In the final state the photocurrents excited by monochromatic light increase with temperature, the relative increase being greater for the longer wave-lengths. At the higher temperatures the spectral sensitivity curves approach the axis asymptotically. The results are shown to be in excellent agreement with Fowler's recent theory and his method of analysis yields the value 4.97\ifmmode\pm\else\textpm\fi{}0.01 volts for the true work function (2486A). The thermionic work function for the clean specimen was found to be 4.99\ifmmode\pm\else\textpm\fi{}0.04 volts, and the value of the constant $A$ is very close to 60 amp./${\mathrm{cm}}^{2}$ ${\mathrm{deg}}^{2}$.