An internal coordinate model of coupling between the torsion and C{endash}H vibrations in methanol
- Department of Chemistry, The University of Akron, Akron, Ohio, 44325-3601 (United States)
The torsional tunneling splittings of the asymmetric C{endash}H stretches ({nu}{sub 2} and {nu}{sub 9}) in methanol are inverted with the {ital E} level lower in energy than the {ital A} level, whereas the symmetric C{endash}H stretch ({nu}{sub 3}) is normal with {ital A} below {ital E}. An internal coordinate model, which treats the torsion and the three C{endash}H stretches simultaneously, accounts for the observed tunneling splittings. The model parameters are the local stretching frequency {omega}=2934.0 cm{sup {minus}1}, the direct local{endash}local coupling {lambda}={minus}42.2 cm{sup {minus}1}, and a single stretch-torsion coupling parameter {mu}=12.9 cm{sup {minus}1}. The torsion-vibration coupling is nonadiabatic in the sense that it is not consistent with a Born{endash}Oppenheimer separation of the torsion from the other vibrations. The fact that the model is based largely on the G{sub 6} molecular symmetry suggests that tunneling inversion may be common in torsional molecules. The torsionally mediated couplings among the C{endash}H stretches do not conserve symmetry in the C{sub s} point group and are strong enough to contribute to rapid intramolecular vibrational redistribution (IVR). {copyright} {ital 1998 American Institute of Physics.}
- OSTI ID:
- 300102
- Journal Information:
- Journal of Chemical Physics, Vol. 109, Issue 24; Other Information: PBD: Dec 1998
- Country of Publication:
- United States
- Language:
- English
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