A complex Gaussian approach to molecular photoionization

TL;DR

This paper introduces a Gaussian-based method for calculating molecular photoionization properties, enabling analytical evaluation of transition integrals and validated through applications to NH3 and H2O molecules.

Contribution

It develops a novel complex Gaussian approach for representing continuum wavefunctions, improving the accuracy and efficiency of photoionization calculations.

Findings

Accurate partial cross-sections computed for NH3 and H2O

Analytical transition integrals facilitate efficient calculations

Method validated against known molecular photoionization data

Abstract

We develop and implement a Gaussian approach to calculate partial cross-sections and asymmetry parameters for molecular photoionization. Optimal sets of complex Gaussian-type orbitals (cGTOs) are first obtained by non-linear optimization, to best fit sets of Coulomb or distorted continuum wave functions for relevant orbital quantum numbers. This allows us to represent the radial wavefunction for the outgoing electron with accurate cGTO expansions. Within a time-independent partial wave approach, we show that all the necessary transition integrals become analytical, in both length and velocity gauges, thus facilitating the numerical evaluation of photoionization observables. Illustrative results, presented for NH3 and H2O within a one-active-electron monocentric model, validate numerically the proposed strategy based on a complex Gaussian representation of continuum states.