Butterfly motion of isolated perylene in its ground and first excited singlet states

Abstract

Vibrational frequencies and Franck-Condon factors derived from laser-induced fluorescence spectra of jet-cooled perylene obtained by Tramer and co-workers are presented for the two lowest-frequency out-of-plane deformation modes. Potential functions are calculated for the “butterfly” mode in the ground and first excited singlet electronic states. The molecule appears to be planar in both cases. A simplified force constant analysis shows that the rigidity of the molecule and the vibrational coupling constant between the two naphthalene entities increase significantly in the excited state.