		15min:

MOLECULAR BEAM INFRARED SPECTRUM OF THE HF STRETCHING FUNDAMENTAL BAND OF
THE HF-BF₃ COMPLEX.

K. NAUTA AND R. E. MILLER, Dept. of Chemistry, University of North Carolina, Chapel Hill, NC 27599; G. T. FRASER AND W. J. LAFFERTY, Optical Technology Division, NIST, Gaithersburg, MD 20899.

The microwave spectrum of the antihydrogen bonded HF-BF₃ complex has recently been reported by Philips et al. . The spectrum reveals a near symmetric F-BF₃ heavy atom frame with the proton slightly off axis, and a small barrier to internal rotation of the H atom against the F atoms. Here, we have investigated the H-F stretching fundamental band of this complex using a molecular beam optothermal spectrometer and a color-center laser. Two subbands are expected: a parallel band with Delta m = 0 selection rules and a perpendicular band with Delta m = \pm 1 selection rules. At present, only the perpendicular band has been observed. This band has the appearance of a perpendicular band of a symmetric rotor, but with anomalously strong ^rR transitions and weak ^pP transitions. Upper state constants are obtained fixing the ground-state constants to the microwave-determined values. The band has a large positive \zeta Coriolis constant, from which an estimate of the barrier to internal rotation can be made. A search is presently underway to locate the expected weaker Delta m=0 parallel component.