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Line Strengths of Torsion-Rotation Transitions of Methanol for J less than or equal} 14 and vt less than or equal} 2 From Hamiltonian Based Calculations

Published

Author(s)

M A. Mekhtiev, P D. Godfrey, Jon T. Hougen

Abstract

Line strengths have been obtained for methanol, based on matrix elements of the dipole moment operator evaluated in a set of torsion-rotation eigenfunctions. The latter were obtained from the parameters and effective Hamiltonian giving the best spectral fit available for a data set containing J less than or equal} 20, K less than or equal} 14 and vt less than or equal} 1 microwave and far infrared transitions. The dipole moment function was represented as a Fourier expansion in the torsional angle γ. Values for the permanent components υa and υb were obtained from experiment; values for their cos3γ variation and for the sin3γ variation of υc were obtained from quantum chemistry molecular orbital calculations. The approach described allows calculation of the line strength for any transition which satisfies the general selection rule A1 <-> A2, or E <->E. A complete set of such line strengths for all methanol torsion-rotation transitions involving levels with J less than or equal} 22, K less than or equal} 14 and vt less than or equal} 2, and with intensities and frequencies above the rather small cutoff limits of 10-6u2 and 1 kHz, respectively, together with individual contributions from the permanent and γ-varying dipole moment components, have been tabulated and are available from the anonymous ftp.monash.edu.au/pub/chem/1998a site.
Citation
Journal of Molecular Spectroscopy

Keywords

infrared spectroscopy, intensity calculations, methanol, microwave spectroscopy, rotational lines, theory

Citation

Mekhtiev, M. , Godfrey, P. and Hougen, J. (1998), Line Strengths of Torsion-Rotation Transitions of Methanol for J {less than or equal} 14 and v<sub>t</sub> {less than or equal} 2 From Hamiltonian Based Calculations, Journal of Molecular Spectroscopy (Accessed June 16, 2024)

Issues

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Created November 8, 1998, Updated October 12, 2021