Collisions of ultracold RbCs molecules*

Ultracold polar molecules offer many exciting opportunities in the fields of quantum computation, quantum simulation and fundamental studies of quantum matter. Long-lived, trapped samples of molecules are crucial to many of these applications. Yet, remarkably, the nature of the collisions between molecules is poorly understood, with fast loss being observed even for chemically stable molecules such as RbCs. Here we report measurements of collisional loss in gases of ultracold RbCs molecules confined in an optical trap. We study both molecule-molecule collisions and atom-molecule collisions. For molecule-molecule collisions we present evidence that pairs of molecules form long-lived collision complexes that are lost due to fast optical excitation by the dipole trapping light. with both Rb and Cs. For atom-molecule collisions we investigate both reactive Rb+RbCs and nonreactive Cs+RbCs collisions, comparing our results to simple single-channel models with short-range loss.