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MICHAEL HIPPLER, LARS OELTJEN AND MARTIN QUACK, Physical Chemistry, ETH Zurich,\linebreak CH-8093 Zurich, Switzerland.
The (HF)2 hydrogen bonded dimer has been a prototype system for high-resolution spectroscopy since the pioneering studies of its microwave spectra by Dyke, Howard, and Klemperer in 1972.1 Subsequently the HF stretching fundamentals were studied in 1983,2 a low frequency fundamental analyzed in the far infrared in 1987,3 HF stretching overtone spectra investigated by FTIR spectroscopy4 and finally full dimensional potential energy hypersurfaces developed of near to spectroscopic accuracy.5,6 All these were "first" achievements prototypical for any type of hydrogen bonded dimer of this kind. Here we present the first study of the N=2 HF stretching overtone polyad by very high resolution cw-diode laser cavity ring-down spectroscopy in pulsed slit jet expansions developed recently7 (instrumental bandwidth about 1 MHz corresponding to a resolving power of 2× 108). An analysis of all polyad subbands in terms of spectroscopic constants, tunneling splittings, Lorentzian predissociation and Doppler contributions to the linewidths will be presented.8 The results agree well with full six-dimensional calculations9 but disagree with simple models or approximate calculations that have been presented in the past.
1~T.~R. Dyke, B.~J. Howard, and W. Klemperer, J. Chem. Phys. 56 (1972), 2442.
2~A.~S. Pine, and W.~J. Lafferty, J. Chem. Phys. 78 (1983), 2154.
3~K. von Puttkamer, and M. Quack, Mol. Phys. 62 (1987), 1047.
4~K. von Puttkamer, and M. Quack, Chem. Phys. 139 (1989), 31.
5~M. Quack, and M.~A. Suhm, J. Chem. Phys. 95 (1991), 28.
6~W. Klopper, M. Quack, and M.~A. Suhm, J. Chem. Phys. 108 (1998), 10096.
7~M. Hippler, and M. Quack, Chem. Phys. Lett. 314 (1999) 273; J. Chem. Phys. (2002) in press.
8~M. Hippler, L. Oeltjen, and M. Quack, in preparation.
9~J. Blumberger, L. Oeltjen, M. Quack, Z. Bacić, and Y. Qiu, in preparation.