Accuracy of molecular data in the understanding of ultracold collisions

We show through close-coupled quantum-scattering calculations that the cross section for fine-structure-changing collisions between excited ${}_{}{}^2{}_{}{}^{}$ ${\mathit{P}}_{3/2}$ and ground ${}_{}{}^2{}_{}{}^{}$ ${\mathit{S}}_{1/2}$ A atoms of the same species, where A=Rb or Cs, is very sensitive to the molecular potentials and spin-orbit matrix elements of the alkali-metal-dimer species. Spectroscopic studies of these species are needed to extract accurate parameters. New high-resolution photoassociation spectroscopy of trapped atoms could be used for this purpose.