Theoretical Study of Triplet—Triplet Absorption Spectra. I. Alternant Hydrocarbon Molecules

Abstract

The self‐consistent‐field molecular‐orbital method of Pariser, Parr, and Pople is utilized to calculate the transition energies and oscillator strengths of triplet—triplet absorption bands in 12 alternant hydrocarbon molecules. The agreement between theory and experiment for the energy of the most intense triplet—triplet absorption band in the visible region of the spectrum is of the order of 0.1 eV. The positions of the weaker bands are calculated less reliably. The axis of polarization calculated for the triplet—triplet bands agrees with experiment in the few cases where such measurements have been made. In addition, the locations of several triplet—triplet bands not yet observed in the infrared and ultraviolet regions are predicted.