Photo-induced two-body loss of ultracold molecules

Arthur Christianen, Martin W. Zwierlein, Gerrit C. Groenenboom, Tijs Karman

Phys. Rev. Lett. 123, 123402 (2019)

The lifetime of nonreactive ultracold bialkali gases was conjectured to be limited by sticky collisions amplifying three-body loss. We show that the sticking times were previously overestimated and do not support this hypothesis. We find that electronic excitation of NaK+NaK collision complexes by the trapping laser leads to the experimentally observed two-body loss. We calculate the excitation rate with a quasiclassical, statistical model employing ab initio potentials and transition dipole moments. Using longer laser wavelengths or repulsive box potentials may suppress the losses.