Picosecond excitation and selective intramolecular rates in supersonic molecular beams. I. SVL fluorescence spectra and lifetimes of anthracene and deuterated anthracenes

Abstract

Fluorescence spectra and decay rate results for jet-cooled anthracene and some deuterated anthracenes excited to single vibronic levels in their S1 manifolds are presented. Consistent with our quantum beat results (see accompanying paper), fluorescence spectra exhibit the manifestations of negligible, then limited, and finally, extensive intramolecular vibrational energy redistribution (IVR), as the vibrational energy in S1 is increased. The decay rate results indicate that the primary decay channel of the anthracenes for S1 vibrational energies of 0 to 5600 cm−1 is a radiationless transition involving a small electronic energy gap. These decay rate results also display manifestations of negligible IVR at low energies and extensive IVR at higher energies. The energy at which the decay rates (time-resolved spectra) indicate extensive IVR is about 1800 cm−1.