OPTIMUM RATIONAL VERSIONS OF EFFECTIVE ROTATIONAL HAMILTONIAN OPERATOR OF THE SYMMETRICAL TOP-TYPE MOLECULE - APPLICATION TO THE PH3 MOLECULE IN THE GROUND-STATE

The construction of optimum versions of a rational expansion of the effective rotational Hamiltonian operator for symmetric top-type molecules in a non-degenerate vibrational state is considered, using as an example molecules with a point group symmetry C3v. The high efficiency of the optimum versions obtained has been demonstrated when applied to the rotational spectrum of PH3 in its ground state.