Calculations on the energy levels of alternant hydrocarbon anions

Abstract

The energy levels of the mono- and di-negative ions of naphthalene, anthracene and tetracene have been calculated by a number of methods. For the mononegative ions the calculations based on the Pariser-Parr-Pople approach give much better agreement with experiment than the Hückel independent electron model. A new assignment of the first weak band in the spectra has been suggested. The calculations on the dinegative ions do not agree so well with experiment, but the amount of data available to test the theories is small.