15min:

R. M. LEES, Department of Physics, University of New Brunswick, Fredericton, N.B., Canada E3B 5A3; LI-HONG XU, Department of Physical Sciences, University of New Brunswick, Saint John, N.B., Canada E2L 4L5.

The Fourier transform spectrum of the CO-stretching fundamental of CH₃OH has been re-examined at higher pressure and path length than heretofore in a study of the lower modes over the 930-1400 cm^-1 region. With the increase in spectral sensitivity, it has been possible to assign a significant number of new subbands for torsionally excited _t = 1 and _t = 2 substates, plus some high-K subbands for the _t = 0 torsional ground state. Assignments have also been extended to higher J for most of the previously known subbands. We have observed a number of new J-localized resonances arising from level-crossings with other torsion-vibration modes. The partner levels have been identified and the interactions characterized for some of the resonances, while others remain mysterious. We are exploring the extent to which the unperturbed CO-stretching levels can be modelled by an effective Hamiltonian of the multi-parameter type used successfully to fit the ground state. So far, 1620 lines have been fitted with a weighted standard deviation of 100 corresponding to a mean residual of approximately 0.02 cm^-1, still some distance from experimental uncertainty.