The electronic structure and spectrum of nitrobenzene

Abstract

Calculations on the electronic spectrum of nitrobenzene are performed by the Pariser-Parr-Pople-Brown-Heffernan method employing five kinds of approximations for the core resonance integrals, penetration integrals and bond lengths. The calculated transition energies and intensities agree fairly well with experiment. It is confirmed that the calculation, using approximate bond lengths, may predict the transition energies well but not the intensities, and that penetration integrals are safely neglected when many configurations are mixed. It is suggested that adoption of fairly large values for core resonance integrals might be needed in the case that many doubly excited states are included in the configuration interaction procedure.