Decoherence via induced dipole collisions in an ultracold gas
Abstract
We have studied the effects of loading 87Rb into a far off resonant trap (FORT) in the presence of an ultracold cloud of 85Rb. The presence of the 85Rb resulted in a marked decrease of the 87Rb load rate. This decrease is consistent with a decrease in the laser cooling efficiency needed for effective loading. While many dynamics which disrupt loading efficency arise when cooling in a dense cloud of atoms (reabsorption, adverse optical pumping, etc.), the large detuning between the transitions of 85Rb and 87Rb should isolate the isotopes from these effects. For our optical molasses conditions we calculate that our cooling efficiencies require induced ground-state coherences. We present data and estimates which are consistent with heteronuclear long-ranged induced dipole-dipole collisions disrupting these ground state coherences, leading to a loss of optical trap loading efficiency.