INTERMOLECULAR VIBRATIONS OF PHENOL-CENTER-DOT(H2O)(3) AND D(1)-PHENOL-CENTER-DOT(D2O)(3) IN THE S-0 AND S-1 STATES

We report a combined spectroscopic and theoretical investigation of th e intel-molecular vibrations of supersonic jet-cooled phenol .(H2O)(3) and d(1)-phenol .(D2O)(3) in the S-0 and S-1 electronic states. Two-c olor resonant two-photon ionization combined with time-of-flight mass spectrometry and dispersed fluorescence emission spectroscopy provided mass-selective vibronic spectra of both isotopomers in both electroni c states. In the S-0 state, eleven low-frequency intermolecular modes were observed for phenol .(H2O)(3), and seven for the D isotopomer. Fo r the S-1 state, several intermolecular vibrational excitations were o bserved in addition to those previously reported, Ab initio calculatio ns of the cyclic homodromic isomer of phenol .(H2O)(3) were performed at the Hartree-Fock level, Calculations for the eight possible conform ers differing in the position of the ''free'' O-H bonds with respect t o the almost planar H-bonded ring predict that the ''up-down-up-down'' conformer is differentially most stable. The calculated structure, ro tational constants, normal-mode eigenvectors, and harmonic frequencies are reported. Combination of theory and experiment allowed an analysi s and interpretation of the experimental S-0 state vibrational frequen cies and isotope shifts. (C) 1995 American Institute of Physics.