Elastic scattering of cold caesium and rubidium atoms

For elastic scattering of Cs atoms by Rb and Rb atoms, interacting via the X Σ and a Σ molecular states of RbCs, calculations are presented of the scattering length and the effective range and also of two volume parameters, one for low energy p-wave scattering and one for the energy of an ensemble of fermions. The calculations are performed by various methods, with several representations of the interatomic potentials, including new ab initio potentials presented here. It is shown how the calculated data may be corrected to include the influence of the long range interactions, thus removing the need for numerical solutions of the radial Schrödinger equation at very large interatomic separations. The sensitivity of the results to the choice of potentials, to the van der Waals dispersion coefficient C and to the reduced mass of the colliding atoms is explored, and is found to be great.