The ²Π_g shape resonance in electron-acetylene scattering: an investigation using the dilated electron propagator method

Abstract

The zeroth order (∑⁰), the second order (∑²), the diagonal two particle-one hole Tamm Dancoff approximation (∑^2ph-TDA) and the corresponding quasi-particle decouplings of the dilated electron propagator have been used to investigate the ²Π_g C₂H₂^- shape resonance. The results compare favourably with the experimental and other theoretical results. A plot of the resonant Feynman-Dyson Amplitudes establishes that the capture of the impinging electron is indeed in the π^∗_g orbital of the acetylene molecule. The resonant orbital on the real line shows the attributes of the acetylene lowest unoccupied molecular orbital and for the optimal complex scaling parameter shows a depletion of electron density near the carbon nuclei.