Basis set, correlation and relaxation effects in the characterisation of electron-molecule scattering resonances using the dilated electron propagator method with application to the ²II_g N₂^- shape resonances

Abstract

The effect of basis set variations on molecular resonance attributes is investigated using systematically augmented basis functions and correlating the resulting changes in resonance energy and width with the alterations induced in the resonant Feynman Dyson amplitudes. Application to the prototypical ²II_g N₂^- shape resonances reveals that basis set effects can be quite large and that

basis sets effecting large 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 offer optimal characterisation of these resonances. A comparison of results from the zeroth order, second order, diagonal 2ph-TDA and quasi-particle decouplings shows that the basis set

effects can be larger than the correlation and relaxation effects and systematic basis set saturation is required for dependable characterisation of molecular resonances.