Spectroscopic determination of the s-wave scattering length of lithium.

E. R. I. Abraham, W. I. McAlexander, C. A. Sackett, and Randall G. Hulet Physics Department and Rice Quantum Institute, Rice University, Houston, Texas 77251-1892 (Received 2 September 1994) Two-photon photoassociation of colliding ultracold Li atoms is used to probe the Su sad ground state of Li2. The binding energy of the least-bound state of this triplet potential, y ­ 10, is found to be 12.47 6 0.04 GHz. This spectroscopic information establishes that the s-wave scattering length for Li atoms in the F ­ 2, mF ­ 2 state is s227.3 6 0.8da0. The negative sign of the scattering length has important implications as to whether atoms at this doubly spin-polarized state can undergo a BoseEinstein condensation.