Optical properties and electronic structures of alpha - and gamma -Ce.

Abstract

The optical properties of metallis \ensuremath{\alpha}- and \ensuremath{\gamma}-Ce were investigated by spectroscopic ellipsometry in the energy range 1.5--5.4 eV. The samples were thin films deposited in situ at room temperature and at 25 K for \ensuremath{\gamma}- and \ensuremath{\alpha}-Ce, respectively. The measured conductivities decrease in magnitude as the thickness increases, which can be explained with a microscopic surface roughness model. The optical conductivity increases upon entering the \ensuremath{\alpha} phase because of the increased number of electrons per unit volume due to the volume collapse. The energy band structures and the optical conductivities were calculated using the linearized-augmented-plane-wave (LAPW) method within density-functional theory, treating both the 4f and 5p electrons as bandlike. The application of the partial sum rule to angular-momentum-decomposed optical conductivities shows that the 4f electron contributions in the measured energy range is small.