Linestrengths of Torsion-Rotation Transitions of Methanol for J </= 22, K </= 14, and upsilont </= 2 from Hamiltonian-Based Calculations.

Linestrengths 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 </= 20, K </= 14, and upsilont </= 1 microwave and far infrared transitions. The dipole moment function was represented as a Fourier expansion in the torsional angle gamma. Values for the permanent components µa and µb were obtained from experiment; values for their cos 3gamma variation and for the sin 3gamma variation of µc were obtained from quantum chemistry molecular orbital calculations. The approach described allows calculation of the linestrength for any transition which satisfies the general selection rule A1 left and right arrow A2 or E left and right arrow E. A complete set of such linestrengths for all methanol torsion-rotation transitions involving levels with J </= 22, K </= 14, and upsilont </= 2, and with intensities and frequencies above the rather small cutoff limits of 10(-6) D2 and 1 kHz, respectively, together with individual contributions from the permanent and gamma-varying dipole moment components, have been tabulated and are available on request (ftp.monash.edu.au/pub/chem/1998a). Copyright 1999 Academic Press.