MATRIX-ISOLATED HF - THE HIGH-RESOLUTION INFRARED-SPECTRUM OF A CRYOGENICALLY SOLVATED HINDERED ROTOR

The spectra of the infrared fundamentals of HF and DF isolated in soli d Ar were recorded at high resolution, and general agreement with prev ious measurements was found. The temperature behavior of the spectra s how that both species are nearly free rotors, in agreement with previo us observations. The positions and splittings of these features, howev er, show that the rotation is at least slightly hindered and that more than one matrix site is observed. These spectra have been simulated u sing recent ArHF and Ar-2 intermolecular potentials in a calculation o f the rotational energy states of various matrix sites. The Hutson H6( 4, 3, 2) potential gives reasonable to excellent agreement between the predicted and observed features, including the redshift from the gas phase to the matrix, and the spectra are interpreted in terms of two s ites: a single substitution site, which perturbs the rotational spectr um slightly, and a distorted interstitial site which is more hindering .