REDUCED EFFECTIVE HAMILTONIAN FOR A GLOBAL TREATMENT OF ROVIBRATIONAL ENERGY-LEVELS OF NITROUS-OXIDE

An effective Hamiltonian has been used for a global treatment of rovibrational energy levels of a given isotopic species of N2O. This Hamiltonian has been written up to the fourth order in the Amat-Nielsen ordering scheme and contains all resonance interaction terms due to the approximate relations between harmonic frequencies omega(3) approximate to 2 omega(1) approximate to 4 omega(2). It has been found that the effective Hamiltonian under consideration possesses some ambiguities. To remove them the effective Hamiltonian has been transformed to a reduced form. Several reduced forms of the effective Hamiltonian have been considered, and the relations between the parameters of the transformed and untransformed effective Hamiltonians have been established. The parameters of the reduced effective Hamiltonians have been determined by a least-squares fit of the experimental values of effective spectroscopic constants G(n)u, B(n)u, and D(n)u. Different reduction schemes are investigated, and extrapolational properties of the corresponding effective Hamiltonians are briefly discussed. (C) 1994 Academic Press, Inc.