Jet-cooled naphthalene. II. Single vibronic level fluorescence spectra

Single vibronic level fluorescence spectra have been measured for naphthalene cooled in a supersonic free jet. Ten spectra in all have been recorded, the excitation energies ranging from 0 to 4029 cm−1 above the 1B3u(ππ*)←1Ag origin. These results reveal extensive intramolecular vibrational redistribution (IVR) occurring in the absence of collision on a time scale much faster than fluorescence even at vibrational energies as low as 2570 cm−1. Comparison of the observed spectra with model calculations shows that this IVR process involves most of the harmonic overtone/combination basis states of overall b1g symmetry having energies within the absorption line profile.