Optical reflectivity of neptunium and plutonium monochalcogenides under high pressure

Abstract The near-normal incidence optical reflectivity of cubic AnX-compounds (An  Np, Pu; X  S, Se, Te) has been measured in the energy range 0.5–5 eV at room temperature as a function of pressure. Reflectivity versus energy curves are relatively smooth for the neptunium compounds, whereas sharp maxima are observed for the plutonium compounds. By comparison with results on corresponding uranium analogs the two main contributions to the optical response near 1–2 eV and above 3 eV could be identified as transitions from hybridized p-5f and p valence band to crystal field split 6d conduction band states.