Mujian Liu

An internal axis approach for the internal rotation problem in asymmetric-asymmetric molecules: Application to the microwave torsional-rotational spectra of CH2DOH and CHD2OH

Abstract The IAM theory of the previous paper is used to calculate the torsional-rotational term values for CH 2 DOH and CHD 2 OH that have been observed experimentally. The Cal. — Obs. differences are found to contain predominantly rigid rotor terms that cannot be developed from the molecular structure. These terms have their origin in the interaction of internal rotation and rotation with the other vibrations of the molecules. A slightly modified molecular structure, due to the deuterium substitution, is determined for each species from the analysis. The best potential energy coefficients are CH 2 DOH CHD 2 OH V 1 = 8.80 cm −1 V 1 = −9.21 cm −1 V 2 = 2.42 cm −1 V 2 = −2.29 cm −1 V 3 = 373.22 cm −1 V 3 = 373.28 cm −1

An internal axis approach for the internal rotation problem in asymmetric-asymmetric molecules: Theoretical formulation

Abstract An internal axis (IAM) formulation for internal rotation in molecules has been developed when both the top and frame have planes of symmetry. The rotational coefficients are expanded in Fourier series after the internal axis system has been defined by coordinate transformations. The final form of the Hamiltonian has an extremely clean form which is suitable for computer solution. In the accompanying paper the theory is applied to the analysis of the microwave torsional-rotational spectra of CH 2 DOH and CHD 2 OH and then in a second paper to the prediction, assignment, and analysis of the spectrum of CHD 2 OD.

The microwave torsional-rotational spectrum of CHD2OD

Abstract The microwave torsional-rotational spectrum of CHD 2 OD has been predicted, identified, assigned, and analyzed to determine the internal rotation potential energy coefficients and nonrigidity corrections for the molecule. Although trans to gauche transitions are too weak for observation in the torsional ground states, transitions have been observed within and/or between three excited torsional states as well as the usual gauche (+) to gauche (−) transitions for the torsional ground states. Taken together, these allow for the determination of the potential energy coefficients. The potential energy coefficients for CHD 2 OD are V 1 = −8.73 ± 0.05 cm −1 , V 2 = −2.90 ±0.10 cm −1 , and V 3 = 365.00 ± 0.25 cm −1 .