Molecular Photoionization and Photodetachment Cross Sections Based on L$$^$$ Basis Sets: Theory and Selected Examples

A detailed description of a method proposed to compute total photoionization and photodetachment cross sections of atoms and molecules relying just on L\(^2\) basis sets is presented. The method consists of an analytical continuation procedure based on Padé approximants. It has the advantage of treating the discrete and continuum part of the spectra at the same level with a flexible choice of the correlated electronic structure approximations. Herein, we present results obtained at the coupled cluster singles and doubles (CCSD) and time-dependent density functional theory (TDDFT) level. Examples of L\(^2\) basis sets adequate and inadequate to reproduce the continuum region of the spectrum are given for the CCSD photoionization cross section of He. Also, a brief review of recent applications of the method is presented, together with original TDDFT results for the total photoionization cross section of formic acid, HCOOH, and the photodetachment cross section of the formate anion, HCOO\(^-\).