Collisions of Ultracold Trapped Cesium Feshbach Molecules

TL;DR

This paper investigates ultracold cesium molecule collisions in optical traps, revealing narrow resonances and complex temperature-dependent loss behaviors that suggest intricate molecular structures beyond simple dimer interactions.

Contribution

It reports the observation of narrow loss resonances and unusual temperature dependence in ultracold Cs$_2$ molecule collisions, indicating complex molecular states and interactions.

Findings

Identification of narrow loss resonances

Observation of temperature-dependent collisional loss

Evidence for complex molecular structures beyond simple dimers

Abstract

We study collisions in an optically trapped, pure sample of ultracold Cs$_2$ molecules in various internal states. The molecular gas is created by Feshbach association from a near-degenerate atomic gas, with adjustable temperatures in the nanokelvin range. We identify several narrow loss resonances, which point to the coupling to more complex molecular states and may be interpreted as Feshbach resonances in dimer-dimer interactions. Moreover, in some molecular states we observe a surprising temperature dependence in collisional loss. This shows that the situation cannot be understood in terms of the usual simple threshold behavior for inelastic two-body collisions. We interpret this observation as further evidence for a more complex molecular structure beyond the well-understood dimer physics.