Photoelectric Properties of Natural Uranium and Changes Occurring at Crystallographic Transformations

Abstract

Studies of the photoelectric properties of high-purity, carefully outgassed natural uranium were made through a wide temperature range, including the temperatures 938\ifmmode^\circ\else\textdegree\fi{}K and 1043\ifmmode^\circ\else\textdegree\fi{}K at which crystallographic transformations occur. Changes in the slope of the temperature-photoelectric current curves for various monochromatic radiations are presented. Analysis of the data at different temperatures by the method of Fowler indicates changes in both the surface work function and the combined number density of free electrons and transition probability factor at the allotropic transformation temperatures. The work function of "clean" uranium was found to be 3.47 ev, 3.52 ev, and 3.39 ev, respectively, for orthorhombic (below 938\ifmmode^\circ\else\textdegree\fi{}K), tetragonal (938\ifmmode^\circ\else\textdegree\fi{}K to 1043\ifmmode^\circ\else\textdegree\fi{}K) and body-centered cubic (above 1043\ifmmode^\circ\else\textdegree\fi{}K) uranium.