High resolution fourier transform far infrared spectroscopy of CH₃OD

Abstract

The high resolution Fourier transform far infrared spectrum of the torsion rotation band of CH₃OD has been recorded in the range 20-350 cm^-1at a resolution of 0.002 cm^-1. The spectrum shows splitting of the lines due to strong torsional, rotational, and vibrational interactions in the molecule. Assignments were possible for rotational subbands in the ground torsional state (n= 0) forKvalues up to 15 andJvalues of up to 30, for all the symmetry species. In addition, some subbands were also identified which involve torsionally excited states. A total of 63b-type subband origins, including 6Q-branch origins obtained from microwave (MW) and millimeter-wave (MMW) studies, were fitted to a semiempirical model. The molecular parameters so determined were able to reproduce the subband origins almost to within experimental uncertainty. The torsional-rotational state-dependent effective molecular parameters and the asymmetry splitting parameters have also been determined. These should prove valuable in the assignment of transitions involving torsionally excited states in the ground vibrational state.