On effective non-rigid gyroscope method for polyatomic molecules

Proceeding from the general formulae of perturbation theory, the author has developed a procedure which makes possible a patial diagonalization of the rotational-vibrational Hamiltonian of a molecule in the vibrational quantum numbers of the nondegenerate vibrational state. Formulae have been obtained for a complete rotational-vibrational wave function and an 'effective' rotational Hamiltonian which is constructed in such a way that the total energy is the sum of the vibrational and rotational energies