Vibration–Internal Rotation–Overall Rotation Interactions in CH2DOH and CHD2OH: I. Development and Application of the Separation Transformations to the Zeroth-Order Kinetic Energy

The zeroth-order kinetic energy is developed for the vibrating–rotating–internally rotating CH2DOH and CHD2OH molecules using the general theory of Guan and Quade for the vibration–rotation–large amplitude internal motion interactions in molecules. A T transformation is applied to obtain the necessary (G−1)0 vibrational matrix elements in the kinetic energy for the R transformation that separates the internal rotation from the 3N–7 other vibrations. Then, a second T transformation is used to separate rotation from the 3N–7 other vibrations in zeroth order in the kinetic energy. The overall rotation and internal rotation remain coupled in zeroth order. All zeroth-order kinetic energy coefficients are calculated from the molecular structure and masses for the methyl alcohol molecules. The physical significance of the transformations is discussed in detail. This paper reports the results of the first segment of the three segments that are necessary in the calculation of the full solution to the problem.