  Results for elastic atom-atom scattering are obtained as a first practical
application of RmatReact, a new code for generating high-accuracy scattering
observables from potential energy curves. RmatReact has been created in
response to new experimental methods which have paved the way for the routine
production of ultracold atoms and molecules, and hence the experimental study
of chemical reactions involving only a small number of partial waves. Elastic
scattering between argon atoms is studied here. There is an unresolved
discrepancy between different argon-argon potential energy curves which give
different numbers of vibrational bound states and different scattering lengths
for the argon-argon dimer. Depending on the number of bound states, the
scattering length is either large and positive or large and negative.
Scattering observables, 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 scattering treatment yields resonances which are slightly
lower in energy and narrower than previous determinations using the same
potential energy curve.
