Collisions between Ultracold Molecules and Atoms in a Magnetic Trap

We prepare mixtures of ultracold CaF molecules and Rb atoms in a magnetic trap and study their inelastic collisions. When the atoms are prepared in the spin-stretched state and the molecules in the spin-stretched component of the first rotationally excited state, they collide inelastically with a rate coefficient k(2) = (6.6 +/- 1.5) x 10(-11) cm(3)/s at temperatures near 100 mu K. We attribute this to rotation-changing collisions. When the molecules are in the ground rotational state we see no inelastic loss and set an upper bound on the spin-relaxation rate coefficient of k(2) < 5.8 x 10(-12) cm(3)/s with 95% confidence. We compare these measurements to the results of a single-channel loss model based on quantum defect theory. The comparison suggests a short-range loss parameter close to unity for rotationally excited molecules, but below 0.04 for molecules in the rotational ground state.

Automated summary

In this study, mixtures of ultracold CaF molecules and Rb atoms were prepared in a magnetic trap for analyzing their inelastic collisions. The results indicate that the nature of collisions varies depending on the rotational states of the molecules involved.