Reduced sextic rotational Hamiltonian for C3 v molecules that are quasi-spherical tops (AsH 3, PH 3, OPF 3)

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.