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 in the 3 mu m region IR-absorption spectra of the OH-stretch vibrations of the water molecules in the complex could be recorded. These spectra show that the water molecules are attached as subclusters to the fluorobenzene 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 free water clusters. Further, the IR-depletion spectra allow the assignment of the neutral precursor of the intra-cluster reaction product phenol(+) which is produced in a nucleophilic substitution reaction after the ionization of (fluorobenzene) . (water)(n) complexes.