Photoionization and Auger Spectra from RASPT2/DFT-Bspline Bound-Continuum Approaches

Photoionization and Auger Spectra from RASPT2/DFT-Bspline Bound-Continuum Approaches Bruno N. C. Tenorio, Sonia Coriani, Piero Decleva Modeling processes involving electrons in the continuum are extremely challenging, since the asymptotic behavior of the continuum wave function is poorly described within correlated methods based on quadratically integrable finite basis sets (L2 basis sets), commonly used for bound states. Thus, besides an accurate bound state description, which nowadays can be obtained in many ways (Coupled-Cluster, ADC, MR-CI, RASPT2 etc.) one also need an accurate description of the electron in the continuum. A theoretical model to compute the accurate photoionization dynamical parameters (cross-sections, asymmetry parameters and orbital, or cross-section, ratios) from Dyson orbitals obtained with the multi-state complete active space perturbation theory to the second order (MS-CASPT2) method, and the electronic continuum obtained with a multicentric B-spline basis at the DFT and TD-DFT levels is presented [1]. For the Auger spectra calculation, a projection technique based on the one center approximation (OCA) is implemented within OpenMolcas [2]. One of the advantages of our approach is that by projecting the intensities on the atomic center bearing the core hole and using precalculated atomic radial two-electron integrals, the Auger decay rates can be easily obtained directly with OpenMolcas, avoiding the need to interface it with external programs to compute matrix elements with the photoelectron wave function [3]. [1] Tenorio et al., Molecules 2022, 27, 1203 (https://doi.org/10.3390/molecules2704...) [2] Tenorio et al., submitted 2022, doi: 10.26434/chemrxiv-2022-cz4fr [3] Tenorio et al., J. Chem. Phys. 2021, 155, 131101 (doi:10.1063/5.0062130)