EVIDENCE FOR THE (HF)5 COMPLEX IN THE HF STRETCHING FTIR ABSORPTION-SPECTRA OF PULSED AND CONTINUOUS SUPERSONIC JET EXPANSIONS OF HYDROGEN-FLUORIDE

Preliminary IR-spectroscopic evidence for the (HF)5 complex in supersonic jet expansions of hydrogen fluoride (neat and seeded with He) is presented. A wide range of effective temperatures between 230 and 60 K, as calibrated by HF rotational temperature, could be obtained using a standard continuous jet and a novel technique using asynchronously pulsed jets in conjunction with continuous interferogram detection and random averaging. Extrapolating band maxima to 0 K we find nu = 3245 cm-1 for the HF stretching band assigned to (HF)6 and 3300 cm-1 for (HF)5. The bandwidths are about 20 cm-1 (fwhm). The results are discussed in relation to ab initio calculations, predictions from our recent HF polymer potential models, matrix spectroscopy data and HF vibrational energy transfer.