Dramatic reductions in inelastic cross sections for ultracold collisions near Feshbach resonances

TL;DR

This paper demonstrates that near Feshbach resonances, ultracold inelastic collision rates can dramatically decrease, potentially reaching near-zero levels, which is significant for cooling molecules.

Contribution

It reveals that inelastic cross sections can decrease near Feshbach resonances, contrary to previous expectations, and details the asymmetric oscillations of scattering lengths during tuning.

Findings

Inelastic collision rates can be minimized near Feshbach resonances.

Real and imaginary parts of scattering length oscillate asymmetrically.

Potential for near-zero inelastic collision rates to aid molecular cooling.

Abstract

We show that low-energy inelastic cross sections can decrease as well as increase in the vicinity of a zero-energy Feshbach resonance. When an external field is used to tune across such a resonance, the real and imaginary parts of the scattering length show asymmetric oscillations, with both peaks and troughs. In favorable circumstances the inelastic collision rate can be reduced almost to zero. This may be important for efforts to achieve evaporative and sympathetic cooling for molecules.