A theoretical study of the electronic spectra of pyridine and phosphabenzene

Abstract

The electronic excitation spectra of pyridine and phosphabenzene have been studied using theoretical methods. The electronic states are described by wave functions derived from second-order perturbation theory based on multiconfigurational reference functions. The study includes singlet and triplet valences excited states as well as a number of Rydberg states. For both molecules the transition energies to the two lowest π → π* excited singlet states are known from experiment and reproduced with an accuracy of 0.15 eV or better, while then → π* transition energies are predicted with a somewhat uncertain error of about 0.2 eV. The calculations suggest the lowestn → π* transition detected experimentally in pyridine corresponds to an adiabatic transition. 43 electronic states have been determined in each of the molecules.