Performance of polynomial Gaussian functions in describing the molecular electronic continuum

Abstract

The continuum molecular orbitals arising from L 2 calculations using special polynomial Gaussian functions are accurately tested to probe their capability in producing accurate photoemission cross sections. The molecular potential is represented by the local Xα approximation, which permits a comparison with numerically integrated (exact) orbitals. Several strong anisotropic molecules are taken into account to check the flexibility of the L 2 bases in the presence of strong attractive potentials. This work shows that for adequate choices of Gaussian functions, phase shifts may be estimated with reasonable accuracy while the errors in the continuum transition probabilities are within 2-3% in the more unfavourable cases. Therefore, the proposed basis sets appear to be suitable for the description of the electronic continuum in molecular photoionization calculations.

Hybrid Gaussian–B-spline basis for the electronic continuum: Photoionization of atomic hydrogen

“…Consequently, continuum orbitals obtained numerically from Gaussian functions can only be reliable either in a limited radial domain or within few eV from threshold opening [13][14][15]. Nevertheless, Gaussian functions have been rather successful in describing one-photon ionization of molecules to first order of perturbation theory [16][17][18][19][20][21], since the very localized nature of the ground state effectively restricts the spatial region in which ionization is produced. A similar restriction does not apply to above-threshold ionization (ATI) or to ionization beyond the perturbative regime, thus making the use of Gaussian functions unsuitable for the description * luca.argenti@uam.es of many ultrafast phenomena in the electronic continuum of molecules.…”