ON THE ASSIGNMENT OF A SIZE-SPECIFIC, INTRACLUSTER ION MOLECULE REACTION WITH IR-DEPLETION SPECTROSCOPY/

A combination of IR-depletion and resonant two photon ionization (R2PI ) spectroscopy is used to study molecular aggregates of (fluorobenzene ) . (water)(n). Through the measurement ment of IR-depletion spectra i n the 3 mu m region IR-absorption spectra of the OH-stretch vibrations of the water molecules in the complex could be recorded. These spectr a show that the water molecules are attached as subclusters to the flu orobenzene chromophore. A comparison with (benzene) . (water)(n) and ( water)(1,2) complexes shows that only a minor perturbation is imposed on the water-subcluster through the aromatic ring and that this double resonance technique yields detailed information on the structure of f ree water clusters. Further, the IR-depletion spectra allow the assign ment of the neutral precursor of the intra-cluster reaction product ph enol(+) which is produced in a nucleophilic substitution reaction afte r the ionization of (fluorobenzene) . (water)(n) complexes.