Electronic Structure and Optical Absorption of Liquid Sodium

Motivated by the experimental observation of Mayer and co-workers that the marked structure which occurs in the optical absorption of alkali metals persists into the liquid state, numerical calculations of the eigenstates and optical conductivity of liquid sodium have been performed to investigate whether the main peak in the liquid interference function $a\mathrm{}\left(K\right)\mathrm{}$ gives rise to a liquid analog of the interband transition. The formalism of Faber has been applied, using a pseudopotential due to Animalu and Heine and an interference function due to Ashcroft and Lekner. The peak in $a\mathrm{}\left(K\right)\mathrm{}$ leads to an enhancement of the absorption at high frequencies, but is too wide to give any definite threshold or structure.