Autoionizing excited states of N2 using complex-basis function spin-flip coupled cluster theory

Abstract

Collision-induced autoionizing excited states play an important role in plasma formation through associative ionization, where excited states lie in resonance with the continuum. In this work, we compute the autoionization widths of various doubly excited states of the N2 molecule using equation-of-motion coupled-cluster theory combined with complex basis functions. This study represents the first application of spin-flip methods to doubly excited autoionizing states, enabled by a newly developed computational protocol based on Kaufmann basis functions. We apply this protocol to N2 and determine the widths of the Σg+3, 3–43Πu, and 23Δg states, which are potential contributors to the associative ionization process. Our results establish the complex basis function-based spin-flip method as a reliable and systematically improvable approach for resonance width calculations, opening avenues for its application to a broader class of autoionizing states in molecular systems.