SELF-CONSISTENT MANY-BODY THEORY OF PI-ELECTRON SYSTEMS .2. SELF-ENERGY EFFECTS

In the framework of the theory presented in a preceding paper (I) we analyze the electron self-energy (SE) effects on the low energy spectrum and oscillator strength of ethylene molecule. The SE is expressed through the same degrees of freedom (the one-body and two-body Green's functions) of the local field corrections (LFC) terms, which have been studied separately in I. The SE and LFC corrections are thus calculated by means of a self-consistent procedure. All the calculations are carried out in the Pariser-Parr-Pole (PPP) model. The results show that the SE terms play a decisive role in the self-consistent conditions, at least for the coupling constant g ≳ 1. © 1979 American Institute of Physics.