Photoelectric Effect in Uranium

We report the work function Φ for single and polycrytalline α-uranium over the temperature range 173 ≤ T ≤873 K. Photoemission spectroscopy (PES) measurements were made at energies 21 eV and 40 eV. Surfaces were prepared in situ by sputter/annealing cycles under UHV conditions. Like most metals the polycrystalline specimens showed little temperature dependence, the change in the work function ΔΦ= 1%. Conversely the single crystal changed by 5% over the same temperature range. A sudden temperature arrest in ΔΦ centered at 500 K was detected in the single crystal. This arrest coincides with the ductile-to-brittle (dilation change) transformation temperature.