Spectral band shapes and absorption coefficients for electronic transitions

Abstract

The spectral band shapes of electronic transitions corresponding to the case in which the Franck-Condon principle holds and the case in which the electronic transitions are symmetry-forbidden but vibronic-allowed have been investigated. Semiempirical equations for calculating the absorption coefficients of these two cases have been derived. In order to test this theory and demonstrate its application, the absorption spectra of acetone and cis-stilbene have been calculated and compared with the corresponding experimental spectra. Agreement is satisfactory.