AN ACCURATE NEW POTENTIAL FUNCTION FOR GROUND-STATE Xe2{\rm e}_2 FROM UV AND VIRIAL COEFFICIENT DATA

Author Institution: Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, CanadaDetermining accurate analytic pair potentials for rare gas dimers has been a longstanding goal in molecular physics. However, most potential energy functions reported to date fail to optimally represent the available spectroscopic data, in spite of the fact that such data provide constraints of unparalleled precision on the attractive potential energy wells of these species. A recent study of ArXe showed that it is a straightforward matter to combine multi-isotopologue spectroscopic data (in that case, microwave, and high resolution UV measurements) and virial coefficients in a direct fit to obtain a flexible analytic potential function that incorporates the theoretically predicted damped inverse-power long-range behaviour.\ {\bf 264}, 83 (2010).}~ The present work reports the application of this approach to Xe$_2$, with a direct fit to high resolution rotationally resolved UV emission data for $\,v''\!=\!0\,$ and 1,\ {\bf 82}, 750 (2004).} band head data for $\,v''\!=\!0-9$,\ {\bf 61}, 4880 (1974).} and virial coefficient data for $\,T\!=\!165-950$\,K, edited by M.\ Frenkel and K.N.\ Marsh, Vol.\ 21 (2003).} being used to obtain an accurate new potential energy function for the ground state of this Van der Waals molecule. Analogous results for other rare-gas pairs will also be presented, as time permits

A new empirical potential energy function for Ar₂

<p>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 <i>ab initio</i> 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  <i>r</i>_<i>e</i> = 3.766 (±0.002) Å, while the ⁴⁰Ar <i>s</i>-wave scattering length is −714 Å.</p