Infrared-ultraviolet double-resonance spectroscopy has been applied to discriminate rotamers of jet-cooled aryl alcohol homologues, φ-(CH 2 ) n OH, where φ represents phenyl group and n ) 1, 2, and 3 correspond to benzyl, phenethyl, and 3-phenylpropyl alcohols, respectively. Experimental results indicate that different OH stretching frequencies are associated with different rotamers and that the ability of intramolecular hydrogen bonding with the benzene π-electron decreases with an increase in alkyl chain length. In each aryl alcohol, the most prominent species in jets corresponds to the non-hydrogen-bonded rotamer having higher OH stretching frequency.

IR spectra of the OH stretching vibrations of 2-naphthol-B (B ) H 2 O and CH 3 OH) clusters in S 1 have been measured by photofragment detected IR spectroscopy (PFDIRS). In this spectroscopy, a tunable IR light pulse excites the OH stretching vibration of the electronically excited 2-naphthol-B, which is prepared by a UV light pulse. The vibrationally excited cluster immediately predissociates to generate a 2-naphthol fragment in S 1 . By monitoring the emission only from the 0 0 0 band of the fragment with a monochromator while scanning the IR frequency, a background free IR spectrum of the OH stretching vibration of the cluster in S 1 has been successfully obtained. By comparing the IR spectra of the cluster in S 1 with those of in S 0 , the effect of the electronic excitation on the frequency change of the OH stretching vibration in the cluster is discussed.