Vibronic structure of the emission spectra from single vibronic levels of the S1 manifold in naphthalene: Theoretical simulation

The vibrational structure of electronic spectra of naphthalene is simulated by means of a perturbative calculation of the intensities, based on the vibronic basis set. The formalism is implemented to include the contribution of Herzberg–Teller induced activity for totally symmetric modes and to describe the interference between the latter and the allowed Franck–Condon intensity. Geometries, vibrational normal modes, and vibronic coupling parameters required to model the spectra are obtained by means of ab initio and semiempirical calculations. The structure of absorption and single vibronic level fluorescence spectra is reproduced in detail and consistently for all the spectra examined. It is shown that the intensity of modes ν8a and ν5a is strongly affected by interference effects, and that Dushinsky mode mixing of totally symmetric modes plays a major role in redistributing the intensity among the vibronic bands of the spectra.