title: Deviation from universality in collisions of ultracold 6Li2 molecules.
abstract: Collisions of 6Li2 molecules with free 6Li atoms reveal a striking deviation from universal predictions based on long-range van der Waals interactions. Li2 closed-channel molecules are formed in the highest vibrational state near a narrow Feshbach resonance and decay via two-body collisions with Li2, Li, and Na. For Li2 + Li2 and Li2 + Na, the decay rates agree with the universal predictions of the quantum Langevin model. In contrast, the rate for Li2 + Li is exceptionally small, with an upper bound 10 times smaller than the universal prediction. This can be explained by the low density of available decay states in systems of light atoms [G. Quéméner, J.-M. Launay, and P. Honvault, Phys. Rev. A 75, 050701 (2007)], for which such collisions have not been studied before.
authors.affiliation: MIT-Harvard Center for Ultracold Atoms, Research Laboratory of Electronics, Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. tout@physics.harvard.edu
authors.forename: Tout T
authors.initials: TT
authors.lastname: Wang
authors.forename: Myoung-Sun
authors.initials: MS
authors.lastname: Heo
authors.forename: Timur M
authors.initials: TM
authors.lastname: Rvachov
authors.forename: Dylan A
authors.initials: DA
authors.lastname: Cotta
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ketterle