Intermolecular vibrations of phenol⋅(H2O)3 and d1-phenol⋅(D2O)3 in the S and S1 states

Abstract

We report a combined spectroscopic and theoretical investigation of the intermolecular vibrations of supersonic jet‐cooled phenol⋅(H2O)3 and d 1‐phenol⋅(D2O)3 in the S 0 and S 1 electronic states. Two‐color resonant two‐photon ionization combined with time‐of‐flight mass spectrometry and dispersed fluorescenceemission spectroscopy provided mass‐selective vibronic spectra of both isotopomers in both electronic states. In the S 0 state, eleven low‐frequency intermolecular modes were observed for phenol⋅(H2O)3, and seven for the D isotopomer. For the S 1 state, several intermolecular vibrational excitations were observed in addition to those previously reported. Ab initio calculations of the cyclic homodromic isomer of phenol⋅(H2O)3 were performed at the Hartree–Fock level. Calculations for the eight possible conformers differing in the position of the ‘‘free’’ O–H bonds with respect to the almost planar H‐bonded ring predict that the ‘‘up–down–up–down’’ conformer is differentially most stable. The calculated structure, rotational constants, normal‐mode eigenvectors, and harmonic frequencies are reported. Combination of theory and experiment allowed an analysis and interpretation of the experimental S 0 state vibrational frequencies and isotope shifts.