EXCHANGE-COULOMB MODEL POTENTIAL-ENERGY SURFACE FOR THE N-2-AR INTERACTION

An exchange-Coulomb model potential energy surface has been developed for-the N-2-Ar interaction. This potential energy surface is based upo n recent results for the Heitler-London interaction energy, long-range dispersion energies, the temperature dependencies of interaction seco nd virial, binary diffusion, and mixture shear viscosity coefficients, microwave spectra of the van der Waals complex, and collision broaden ing of the depolarized Rayleigh light scattering spectrum. The adjusta ble parameters in the final potential surface have been determined by fitting the temperature dependence of the virial coefficient (within e xperimental uncertainties) and the frequencies of three representative lines of the microwave spectrum of the N-14(2)-Ar van der Waals compl ex. A fine tuning of these parameters was achieved by considering the temperature dependence of the binary diffusion, and mixture shear visc osity coefficients. Calculated frequencies for all observed microwave transitions of the various N-2-Ar isotopomers lie within 0.1% of the e xperimental values. Excellent agreement is obtained with experimental values of binary diffusion and mixture shear viscosity data for all te mperatures and compositions. Agreement with the bulk gas relaxation ph enomena, while not outstanding, is acceptable, given the accuracy with which these phenomena are currently determinable. Detailed comparison s are made with predictions of the two best literature N-2-Ar potentia l energy surfaces. This new potential surface gives the best overall a greement with experiment for N-2-Ar mixtures. (C) 1995 American Instit ute of Physics.