Experimental investigation of ultracold atom-molecule collisions -: art. no. 023201

Ultracold collisions between Cs atoms and Cs-2 dimers in the electronic ground state are observed in an optically trapped gas of atoms and molecules. The Cs-2 molecules are formed in the triplet ground state by cw photoassociation through the outer well of the 0(g)(-)(P-3/2) excited electronic state. Inelastic atom-molecule collisions converting internal excitation into kinetic energy lead to a loss of Cs-2 molecules from the dipole trap. Rate coefficients are determined for collisions involving Cs atoms in either the F=3 or F=4 hyperfine ground state, and Cs-2 molecules in either highly vibrationally excited states (v(')=32-47) or in low vibrational states (v(')=4-6) of the a (3)Sigma(u)(+) triplet ground state. The rate coefficients beta similar to 10(-10) cm(3)/s are found to be largely independent of the vibrational and rotational excitation indicating unitary limited cross sections.