Wide-range photoabsorption cross-sections of simple metals: large basis-set OPW calculations for sodium

Abstract

Photoabsorption cross-sections of simple metals are formulated through a solid-state band theory based on the orthogonalized-plane-wave (OPW) method in Slater’s local-exchange approximation, where interband transitions of core and conduction electrons are evaluated up to the soft x-ray regime by using large basis sets. The photoabsorption cross-sections of a sodium crystal are computed for a wide photon energy range from 3 to 1800 eV. It is found that the numerical results reproduce the existing x-ray databases fairly well for energies above the L2,3-edge (31 eV), verifying a consistency between solid-state and atomic models for inner-shell photoabsorption; additional oscillatory structures in the present spectra manifest solid-state effects. Our computed results in the vacuum ultraviolet regime (6–30 eV) are also in better agreement with experimental data compared to earlier theories, although some discrepancies remain in the range of 20–30 eV. The influence of the core eigenvalues on the absorption spectra is examined.