Collisions in a dual-species magneto-optical trap of molecules and atoms

Abstract

We study inelastic collisions between CaF molecules and 87Rb atoms in a dual-species magneto-optical trap. The presence of atoms increases the loss rate of molecules from the trap. By measuring the loss rates and density distributions, we determine a collisional loss rate coefficient k 2 = (1.43 ± 0.29) × 10−10 cm3 s−1 at a temperature of 2.4 mK. We show that this is not substantially changed by light-induced collisions or by varying the populations of excited-state atoms and molecules. The observed loss rate is close to the universal rate expected in the presence of fast loss at short range, and can be explained by rotation-changing collisions in the ground electronic state.

Molecule–molecule and atom–molecule collisions with ultracold RbCs molecules

“…We compare the loss rates measured in experiments to a single-channel model based on quantum defect theory (QDT) [65,66]. The model and its underlying theory have been described at length elsewhere [66, 91, 92], so we omit further description here; we have previously applied it to RbCs + RbCs and Rb + CaF collisions [60,75,76]. The long-range interactions are approximated by their leading term −C 6 R −6 and the short-range interactions are modelled by an absorbing boundary condition.…”

“…In this case, atom-molecule combinations (X + XY) can be defined as nonreactive if the atom-exchange reaction X + XY → X 2 + Y is endothermic. However, as was found for molecule-molecule collisions, the reactivity of the combination alone does not appear to determine the rate of collisional loss observed in experiments [34,55,[74][75][76][77][78][79]. For example, reactive atom-molecule collisions in mixtures of triplet 23 Na 6 Li molecules and 23 Na atoms are sufficiently suppressed for the fully stretched hyperfine states that efficient sympathetic cooling of the molecules is possible [74].…”

The Li + CaF → Ca + LiF chemical reaction under cold conditions

“…Stark and Zeeman effects). Additionally, these systems also provide a unique opportunity to improve upon the fundamental understanding of atom-molecule 14 and molecule-molecule interactions, 15 dipolar interactions 16,17 and collision-induced chemistry at the ultra-low range of kinetic energies. [18][19][20][21][22] In particular, experimental explorations of collision-induced trap-loss rate of molecules with singlet and triplet spin multiplicities, in ultracold conditions, have been available for a while (for systems such as Rb 2 , NaRb, KRb, CsRb, NaK, LiNa, NaRb).…”

Tunable Feshbach resonances in collisions of ultracold molecules in $^2Σ$ states with alkali-metal atoms

“…These systems have also been investigated theoretically [34,[38][39][40]. Resonances have not yet been observed in collisions of laser-cooled molecules such as CaF and SrF, with 2 Σ ground states, but we have recently succeeded in making ultracold mixtures of CaF molecules and Rb atoms, and studied their inelastic collisions in both magnetic traps [41] and magneto-optical traps [42]. Several lasercoolable molecules have been cooled to 5 µK [24,25] and confined in optical traps [23] and optical tweezers [43], opening the way to experiments in controlled magnetic fields.…”