Infrared Spectroscopy of the OH Stretching Vibrations of Jet-Cooled Salicylic Acid and Its Dimer in S₀ and S₁

Abstract

Infrared spectra of the OH stretching vibrations of the jet-cooled salicylic acid (SA) monomer and dimer were measured for both their electronic ground (S 0 ) and first excited (S 1 ) states. For the SA monomer, conformations of two rotational isomers (rotamers) which have been identified by the electronic transitions were determined on the basis of the infrared spectra with the help of theoretical calculations. The intramolecular hydrogen-bonded OH stretching vibrations of the monomer showed a drastic change upon the electronic excitation, and it was consistent with the distortion of the H-chelate ring in the S 1 state predicted by theoretical calculations of Sobolewski and Domcke ( Chem. Phys. 1998, 232, 257). Structures of the dimer in the S 0 and S 1 states were also determined by the observation of the OH stretching vibrations. No evidence was found for intermolecular double proton-transfer both in the S 0 and S 1 states of the dimer.