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

## TL;DR

This paper introduces RmatReact, a new computational code for high-accuracy elastic atom-atom scattering calculations, applied here to argon-argon interactions relevant for ultracold chemistry, and compares results with existing data.

## Contribution

The paper presents the first practical application of RmatReact for elastic scattering, demonstrating its effectiveness in calculating scattering observables for ultracold atoms.

## Key findings

- Good agreement with previous results for scattering observables.
- Resonances are slightly lower in energy and narrower than previous calculations.
- Discrepancies in potential energy curves affect scattering length predictions.

## Abstract

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.