CNDO/S studies on the electronic structure of carbazoles. I. The parent molecule

A semi-empirical molecular orbital calculation, using the CNDO/S spectral parameterization of Del Bene and Jaffe, has been carried out for carbazole. The ground state occupied orbital eigenvalues are used to provide an orbital assignment of the photoelectron spectrum of carbazole. A limited configuration interaction procedure, utilizing the lowest 60 singly excited configurations, is subsequently carried out to determine the energies of excited singlet and triplet states of carbazole. Agreement between theoretical calculations and experimental results for the lower lying electronic transitions of carbazole is such as to allow higher lying transitions to be assigned with a degree of confidence.