X-ray absorption spectra from the resonant-convergent first-order polarization propagator approach

Abstract

The one-photon absorption cross sections of molecular systems have been determined in the high-energy region from the imaginary part of the electric dipole polarizability tensor. In contrast to commonly adopted state-specific methodologies, the complex polarization propagator approach does not require explicit consideration of the excited states and it is open-ended towards multiphoton absorption. It is shown that the electronic relaxation in the core-hole state is well accounted for in the present approach with use of standard density-functional based electronic structure methods. Sample calculations are presented of the $K$-edge x-ray absorption spectra for ${\mathrm{H}}_{2}\mathrm{O}$, CO, ${\mathrm{C}}_{4}{\mathrm{H}}_{4}\mathrm{N}$, and ${\mathrm{C}}_{6}{\mathrm{H}}_{6}$.