Fano–Feshbach formalism applied to the calculation of autoionization widths through analytic continuation

Abstract

A method to calculate the autoionization width from a discretized pseudo-spectrum is proposed. The method relies on an analytic continuation of the Green's function within the Fano-Feshbach formalism. The pseudo-spectrum is obtained at multireference Configuration Interaction level in a square-integrable basis set, commonly found in quantum chemistry software. Few states around the desired resonance are needed to perform the analytic continuation. The method was applied to atomic (He and Ne) and molecular (HF and benzene) systems and results for the autoionization width show good agreement with available theoretical and experimental values.