On the physical interpretation of torsion-rotation parameters in methanol and acetaldehyde: Comparison of global fit and {ital ab initio} results

Journal Article · Mon Feb 01 04:00:00 EST 1999 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.478272· OSTI ID:307259

Xu, L ^[1]; Lees, R M ^[2]; Hougen, J T ^[3]

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1. Department of Physical Sciences, University of New Brunswick, Saint John, New Brunswick E2L 4L5 (Canada)
2. Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada)
3. Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

Equilibrium structural constants and certain torsion{endash}rotation interaction parameters have been determined for methanol and acetaldehyde from {ital ab initio} calculations using GAUSSIAN 94. The substantial molecular flexing which occurs in going from the bottom to the top of the torsional potential barrier can be quantitatively related to coefficients of torsion{endash}rotation terms having a (1{minus}cos&hthinsp;3{gamma}) dependence on torsional angle {gamma}. The barrier height, six equilibrium structural constants characterizing the bottom of the potential well, and six torsion{endash}rotation constants are all compared to experimental parameters obtained from global fits to large microwave and far-infrared data sets for methanol and acetaldehyde. The rather encouraging agreement between the Gaussian and global fit results for methanol seems both to validate the accuracy of {ital ab initio} calculations of these parameters, and to demonstrate that the physical origin of these torsion{endash}rotation interaction terms in methanol lies primarily in structural relaxation with torsion. The less satisfactory agreement between theory and experiment for acetaldehyde requires further study. {copyright} {ital 1999 American Institute of Physics.}

• OSTI ID: 307259
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 8 Vol. 110; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
66 PHYSICS
ACETALDEHYDE
INFRARED SPECTRA
METHANOL
MICROWAVE SPECTRA
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
RELAXATION
ROTATIONAL STATES
TORSION