In this communication we wish to report the measurement of photodissociation rates of jet-cooled solute-solvent complexes in various stages of solvation. The observation of fluorescence decays as a function of excess vibrational energy for isoquinoline (IQ), IQ-(methanol)n, and IQ-(water)n complexes reveals threshold behavior for the decays rates of 1:1 solute-solvent complexes. The thresholds at ~3 kcal/mol provide new information on the breakage of excited state hydrogen bonds
