Feshbach projection XMCQDPT2 model for metastable electronic states

TL;DR

This paper introduces a novel computational model combining Feshbach projection and multireference perturbation theory to accurately describe metastable electronic states, including autoionizing states, in polyatomic molecules.

Contribution

It develops a new method integrating Feshbach projection with perturbation theory and absorbing potentials for metastable state modeling.

Findings

Benchmark calculations agree with experimental data

Model effectively describes shape resonances in molecules

Provides a new approach for autoionizing state analysis

Abstract

Autoionizing electronic states are common intermediates in processes initiated by electron impact or high-energy radiation. These states belong to the continuous spectrum of the Hamiltonian, and as such cannot be treated with methods developed for bound electronic states. Here we propose a new model for describing metastable electronic states, which combines discretized Feshbach projection formalism and multireference perturbation theory and exploits absorbing potential to generate the basis of the coupled valence state and continuum. The results of benchmark calculations for a series of shape resonances in polyatomic molecules are in good agreement with experimental and theoretical reference values.