Simplification of the General Quartic Force Field of Linear Triatomic Molecules

A model for the anharmonic interaction force constants of polyatomic molecules, previously advanced by Machida and Overend, has been tested for CO2, CS2, OCS, N2O, and HCN. The parameters of the model have been determined by least squares adjustment to the experimental spectroscopic data, and the results are compared with those found previously with the general quartic force field. The model reduces the number of parameters in the force field of the symmetric molecules from 12 to 7 and the number of parameters in the force field of the unsymmetric XYZ molecules from 19 to 11.