A new empirical potential energy function for Ar₂

A critical re-analysis of all available spectroscopic and virial coefficient data for Ar₂ has been used to determine an improved empirical analytic potential energy function that has been ‘tuned’ to optimise its agreement with viscosity, diffusion and thermal diffusion data, and whose short-range behaviour is in reasonably good agreement with the most recent ab initio calculations for this system. The recommended Morse/long-range potential function is smooth and differentiable at all distances, and incorporates both the correct theoretically predicted long-range behaviour and the correct limiting short-range functional behaviour. The resulting value of the well depth is cm⁻¹ and the associated equilibrium distance is  r_e = 3.766 (±0.002) Å, while the ⁴⁰Ar s-wave scattering length is −714 Å.