Photoemission of surface oxides and hydrides of delta plutonium

High resolution photoelectron spectroscopy (PES) studies were conducted on a gallium stabilized δ-phase plutonium sample cleaned by laser ablation and gas dosed with O2 and H2. The measurements were made with an instrument resolution of 60 meV with the sample at 300 K, 77 K and 10 K. The PES data under these experimental conditions strongly support an idealized model with Pu2O3 growth on the metal followed by PuO2 growth on the Pu2O3 layer at low temperature. In vacuum, the PuO2 reduces to Pu2O3 at room temperature at a pressure of 6 × 10−11 Torr. In the case of H2 dosing of the surface at low temperature, the hydrogen appears to penetrate the surface and disrupt the electronic structure of the valence band as evidenced by a drop in intensity of the peak at EF which is not accompanied by a drop in the main 5f manifold at ∼1 eV. Studies were also carried out on the dosing of hydrogen on surfaces already dosed with both 0.5 L (Pu2O3) and 10 L (PuO2) oxygen films and show that hydrogen penetrates the 0.5 L Pu2O3 covered surface.