INVESTIGATION OF THE TORSION ROTATION ENERGY-LEVELS OF THE CH3 ASYMMETRIC STRETCHES IN METHANOL

The CH3 asymmetric stretching region of methanol vapor has been investigated between 2900 and 3200 cm-1 with a 1.25-m maximum path difference Fourier transform spectrometer. Thirteen P branches and eleven R branches were assigned (13 series representing six excited states belonging to the nu2 fundamental and 11 series representing five excited states belonging to the nu9 fundamental). A nonlinear least-squares analysis of the Q-branch origins for three parameters (the bandcenter, the hindering potential barrier height, and the moment of inertia of the methyl group about the symmetry axis) of the molecule was done. This yielded a bandcenter of 2999.44 cm-1, a barrier height of 405.62 cm-1, and a moment of inertia of 5.29 cm-1 for the nu2 fundamental. The corresponding values for the nu9 fundamental are 2970.18, 529.7 1, and 5.34 cm-1, respectively. The ambiguity of these parameters owing to the relatively small number of identified torsional levels is discussed. (C) 1994 Academic Press, Inc.