An investigation of basis set effects in the characterization of electron – atom scattering resonances using the dilated electron propagator method

 The effects of basis set variations on resonance attributes are investigated using systematically augmented basis sets by correlating the resulting changes in resonance energy and width with the alterations induced in the radial probability density profile of the resonant orbital. Applications to 2P Be− and 2P Mg− shape resonances reveal that basis sets capable of describing both electron density accumulation near the target nucleus to facilitate resonance formation and sufficiently large electron density away from the target nucleus to provide for its decay are necessary for effective characterization of these resonances. A comparison of radial probability density profiles from the bivariational self-consistent field, the second-order, the diagonal two particle–one hole Tamm–Dancoff approximation and quasiparticle decouplings reveals that relaxation effects dominate in resonance formation.