The fluorescence emission spectra of jethyphen;cooled hydrogenhyphen;bonded dimers of benzoic acid and isotopic analogs are presented and the vibrational assignments of the ground state complexes are made. Intramolecular vibrational relaxation is observed inS1at excess vibrational energies as low as 373 cmminus;1. The role of the hydrogen bonding network as a heat bath is considered and the results are consistent with an argument based on an estimate of the density of states. Electronic energy transfer is examined in the weak coupling limit and transfer is observed in mixed dimers of perhydro (d0) and ring deuterated (d5) benzoic acid. Transfer fromd5tod0is observed when excess vibrational energy is present. The jethyphen;cooled, isolated dimer provides an excellent case for the examination of energy transfer in hydrogenhyphen;bonded complexes.
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