Trap loss in a rubidium crossed dipole trap by short-range photoassociation

Abstract

Significant two-body losses are observed in an ultracold gas of 85Rb or 87Rb atoms in a crossed dipole trap implemented with a broadband laser with a wavelength around 1071 nm. Using available spectroscopic data on the excited states of Rb2, as well as accurate computed transition dipole moment functions, we interpret these losses as due to photoassociation of deeply bound levels of the 0+u coupled states by the trapping laser, followed by spontaneous emission down to bound levels of the Rb2 ground state thus forming ultracold molecules. The observed ratio of 3.3 between the loss rates of 87Rb and 85Rb is well reproduced by the theoretical model.