COMPARISON OF TRAP-LOSS COLLISION SPECTRA FOR RB-85 AND RB-87

We present measurements of excited-state trap-loss collisions of optically trapped Rb-85 and Rb-87 atoms as a function of the frequency of the light used to excite the colliding atom pairs. For detunings outside the excited-state hyperfine structure, the trap-loss rates are found to be the same for the two isotopes. For detunings inside the excited-state hyperfine structure, Rb-87 collisions occur at a substantially lower rate than those of Rb-85. The spectra make it clear that the long-range dynamics of the collisions are strongly modified by the excited-state hyperfine structure, and that the dynamics are different for the two isotopes.