Application of higher order decouplings of the dilated electron propagator to ²ΠCO^-, ²Π_gN₂^- and ²Π_gC₂H₂^- shape resonances

Abstract

The full third order (Σ), quasi-particle third order (Σ) and outer valence Green's function (OVGF-A) decouplings of the bi-orthogonal dilated electron propagator have been implemented and results from their application to ΠCO, ΠN, and ΠCH shape resonances are presented and compared with energies and widths obtained using the zeroth order (Σ), quasiparticle second order (Σ) and second order (Σ) decouplings. The energies and widths from the various Σ decouplings for shape resonances are close to those obtained using the Σ approximant but the corresponding Feynman-Dyson amplitudes (FDAs) differ considerably. The differences between FDAs from different decouplings are analyzed to elicit the role of correlation and relaxation in the formation and decay of shape resonances.