Abstract
The static and strain-modulated reflectance of both pure and oxidized gadolinium has been measured for energies from 1.5 to 6.0 eV. The measurements were made in situ in ultra-high vacuum, on polycrystalline films evaporated onto a single-crystal quartz strain transducer. Polarization-resolved measurements were analysed to separate the response into hydrostatic and shear strains. The imaginary part of the hydrostatic component of the modulated dielectric function shows a background signal which is proportional to the frequency derivative of the static dielectric function and gives an average deformation potential of -15 eV per unit hydrostatic strain. Critical-point structure is also seen and assignments are suggested. These structures show some movement with oxidation and a new feature appears at around 5 eV, which moves down in energy with increasing oxidation. This implies the involvement of O 2p bands as initial states, locating the band 5 eV below the Fermi level.