JET SPECTROSCOPY OF THE $2v_{8}$ BAND OF HYDROGEN FLUORIDE TRIMER IN THE $750 CM^{-1}$ REGION
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Date
1998
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Ohio State University
Abstract
Theory predicts a planar ring, oblate symmetric top structure $(C_{3h})$ for hydrogen fluoride trimer. This ground state structure has been confirmed experimentally for deuterium fluoride trimer by Suhm, $et al.^{a}$ and for hydrogen fluoride trimer by Michael and $Lisy.^{b}$ Both of these experiments involved examining intramolecular stretching modes in the cluster. We have recorded what we believe to be the first rotationally resolved spectra of an intermolecular mode: the first overtone of the $\nu_{s}(e^{\prime \prime})$ out-of-plane torsion, which was predicted by Kolenbrander, $et al.^{c}$ This spectrum was produced by expanding a 4\% HF-in-helium mixture through a pulsed, slit-jet source and interrogating the jet with the output of a lead salt diode laser spectrometer. A pressure and concentration study showed that most transitions (FWHM 45 MHz) in the $750 cm^{-1}$ region belong to the same oligimer. Groupings of intense lines are spaced by about $0.284 cm^{-1}$ suggesting a B value of $0.142 cm^{-1}$ which is close to the predicted value of $0.13 cm^{-1}$. The appearance of the spectrum is, however, far more complicated than that predicted for a perpendicular band of a semi-rigid oblate symmetric top.
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$^{a}$ Martin A. Suhm, John T. Farell, Jr., Stephen H. Ashworth, David J. Nesbitt, J. Chem. Phys. 98, 5985 (1993). $^{b}$ Daniel W. Michael, James M. Lisy, J. Chem. Phys. 85, 2528 (1986). $^{c}$ Kirk D. Kolenbrander, Clifford E. Dykstra, James M. Lisy. J. Chem. Phys. 88, 5995 (1988).
Author Institution: Pacific Northwest National Laboratory, P.O. Box 999
Author Institution: Pacific Northwest National Laboratory, P.O. Box 999