Collisions Between Ultracold Molecules and Atoms in a Magnetic Trap

Abstract

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 of $k_2=(6.6\pm 1.5)\times 10^{-11}$ 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 $k_2<5.8\times 10^{-12}$ 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.

9 pages, 6 figures. Minor changes following review

References in corpus (9)

• A High Phase-Space-Density Gas of Polar Molecules
• Observation of Quantum Effects in sub Kelvin Cold Reactions
• Ultracold Rb-OH collisions and prospects for sympathetic cooling
• Laser cooling of molecules
• Cold N+NH Collisions in a Magnetic Trap
• Characteristics of a magneto-optical trap of molecules
• Large Effects of Electric Fields on Atom-Molecule Collisions at Millikelvin Temperatures
• Observation of orbiting resonances in He(3S1) + NH3 Penning ionization
• Controlling Spin-flips of Molecules in an Electromagnetic Trap

Cited by in corpus (2)

• Polarization Enhanced Deep Optical Dipole Trapping of $\Lambda$-cooled Polar Molecules
• Ultracold ${}^{88}{\mathrm{Sr}}_2$ molecules in the absolute ground state