Many-body calculation of electron affinities: C₂ and a prediction for P₂

The electron affinities of the molecules, C₂ and P₂ are calculated by the Green's function formalism which has been successful in determining accurate ionisation potentials of atoms and molecules. The adiabatic electron affinities obtained are AEA(C₂)=3.60 eV and AEA(P ₂)=0.30 eV compared to the experimental values of 3.54 eV and 0.24+or-0.23 eV respectively. The vibrational structure in the radiative electron-attachment spectra of C₂ and P₂ is also computed. There is a close relationship between the vibrational structures in electron-attachment and photodetachment spectra.