On the physical interpretation of torsion-rotational parameters for CH3OD isotopomers

Using the formulation (Phys. Lett. A 207 (1995) 203) of the centrifugal dis tortion effects in terms of the potential parameters for a molecule that co ntains a threefold symmetric internal rotor, molecular parameters have been determined for the C-12 and C-13 isotopomers of CH3OD with O-16, 17 and 18 . The calculated parameters. especially the constants that represent intera ctions between torsion and rotation, are used to interpret the relationship s among the terms in the reduced Hamiltonian and in the analysis of the obs erved torsion-rotational spectrum. Molecular parameters are calculated from several potential energy functions for methanol isotopomers to check the q uality of these potentials. The dependence of torsion-rotational parameters on the mass of atom and the geometric parameters are addressed by comparis ons of calculated values for various isotopomers of CH3OD. The parameters a re compared with the parameters that were obtained from several global fits to experimental spectrum data. The good agreement between the calculated t orsion-rotational parameters and those derived from the global fits demonst rates that the derived formulae provide a useful tool for understanding the physical origins of the Hamiltonian parameters and the dependence of torsi on-rotational parameters on fundamental molecular parameters. (C) 2001 Publ ished by Elsevier Science B.V. All rights reserved.