Low temperature scattering with the R-matrix method: argon-argon scattering.

Results for elastic atom-atom scatteringare obtained as a first practical application of RmatReact, a new code for generating high-accuracy scatteringobservables from potential energycurves. RmatReact has been created in response to new experimental methods which have paved the way for the routine production of ultracold atomsand molecules, and hence the experimental study of chemical reactions involving only a small number of partial waves. Elastic scatteringbetween argonatoms is studied here. There is an unresolved discrepancy between different argon-argon potential energycurves which give different numbers of vibrational bound statesand different scattering lengthsfor the argon-argondimer. Depending on the number of bound states, the scattering lengthis either large and positive or large and negative. Scatteringobservables, specifically the scattering length, effective range, and partial and total cross-sections, are computed at low collision energies and compared to previous results. In general, good agreement is obtained, although our full scatteringtreatment yields resonances which are slightly lower in energy and narrower than previous determinations using the same potential energycurve.