Investigation of electron-induced scattering resonances using a multiconfigurational polarization propagator and a complex absorbing potential

Abstract

We develop a method based on the polarization propagator (PP) combined with the complex absorbing potential (CAP) technique to study metastable resonances induced by electron impact. We use a CASSCF wavefunction corresponding to the ground state of the anion as the initial state for the PP. The perturbation of the Hamiltonian by the CAP allows for complex eigenvalues that represent the continuum states including the resonance buried in the continuum. The artifacts due to the CAP are eliminated using the Padé extrapolation method. We apply our method to study the 2P Be− atomic shape resonance, and 2Πg N2− and 2Π CO− molecular shape resonances. Our estimated resonance positions and widths for the resonances are in agreement with the previously reported values. Overall, this method is a powerful and computationally tractable tool for the study of resonances.