Vibrational energy relaxation of the 7-azaindole dimer in CCl4 solution studied by picosecond time-resolved transient fluorescence detected IR spectroscopy

The picosecond time-resolved IR spectra of the 7-azaindole dimer in a carbon tetrachloride solution was measured by using picosecond time-resolved IR/UV double resonance spectroscopy. This spectroscopy selectively detects the IR transition by transient fluorescence due to an electronic transition from a vibrationally excited level. The time-evolution of the IR spectrum is a single exponential with a 19 ps lifetime, which does not correspond to fast nonstatistical decay due to the intramolecular vibrational redistribution found in a gas-phase cluster. From a comparison with the time-resolved IR spectrum of a jet-cooled dimer, this decay is assigned to vibrational cooling from the dimer to the solvent.