Laser spectroscopic study of intracluster chemical reactions

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1. Spectroscopic studies of the hydrogen-bonding clusters of phenol were reviewed with an emphasis of the characterization of the cluster structures involving the proton transfer processes. Two experimental methods which were newly developed for the spectroscopy of the size selected clusters and their ions were described. Trapped ion photodissociation spectroscopy revealed that chromophore alternation occurs in the cluster cations with various proton-accepting molecules, such as NH_3 and H_2O.The infrared spectroscopy combined with the ionization detection was applied to the spectra of the OH vibrations which characterized the neutral clusters of phenol with water. The spectroscopic evidence of the ion-pair form of the neutral cluster is presented and the possibility of the intracluster acid-base reaction is discussed.2. The OH stretching vibrations of the phenol dimer and trimer prepared in supersonic jets have been observed by IR-UV double-resonance and stimulated Raman-UV double-resonance spectroscopies. In the trimer, all the three OH stretching vibrations showed large red shifts from that of bare phenol. Evidence of the cyclic structure was obtained from an intensity alternation between IR and Raman spectra and by the measurement of the Raman depolarization ratios. In the dimer, it was found that the IR intensity of the OH stretching vibration of the proton-donating phenol is 4 times larger than that of the proton-accepting phenol.