Kamil Sarka

Reduced sextic rotational Hamiltonian for C3v molecules that are quasi-spherical tops (AsH3, PH3, OPF3)

Abstract Reduction of the sextic rotational Hamiltonian for molecules of symmetry C 3 v , that are quasi-spherical tops is carried out. It is shown that the sextic distortion constants are not independent and one of them has to be constrained. This result explains the correlation problems observed in fitting the rotation spectra of AsH 3 and PH 3 . The formulae giving the parameters of the reduced Hamiltonian in terms of the parameters of the unreduced one are also presented.

Ab initio anharmonic force field, molecular parameters, equilibrium structure and enthalpy of formation of fluoroform

The quadratic, cubic and semi-diagonal quartic force field of fluoroform has been calculated at the CCSD(T) level of theory employing a basis set of at least polarized valence triple zeta quality. This force field was used to predict the spectroscopic constants, including the parameters specific to the doubly degenerate vibrational states. The calculated values are not always in good agreement with the experimental data. A careful examination of the calculations and of the experimental spectra indicates that the analysis of some spectra is still not satisfactory because important interactions have been neglected. The equilibrium structure was derived from the experimental ground-state rotational constants and the ab initio rovibrational interaction parameters. This semi-experimental structure is in excellent agreement with the ab initio equilibrium geometry. Finally, an accurate value of the enthalpy of formation of CHF3 was calculated.

Submillimeter-wave spectra of 12CH3F in the v2 = 1 and v5 = 1 vibrational states

Abstract Transition frequencies of the pure rotational transitions in the v 2 = 1 and v 5 = 1 vibrational states of 12 CH 3 F between 180 and 610 GHz have been measured using the submillimeter-wave spectrometer with acoustic detection RAD3. Twenty-two spectroscopic parameters describing the vibration-rotation interactions within and between the v 2 = 1 and v 5 = 1 states have been fitted using a reduced effective Hamiltonian for interacting vibrational states proposed by Lobodenko et al. [J. Mol. Spectrosc. 126 , 159–170 (1987)].