Photoassociation of a Bose-Einstein Condensate near a Feshbach Resonance

TL;DR

This study investigates how a magnetic Feshbach resonance influences photoassociation processes in ultracold lithium, revealing significant magnetic field dependence, saturation effects in BECs, and anomalous frequency shifts.

Contribution

It provides the first observation of saturation in photoassociation rate in a Bose-Einstein condensate near a Feshbach resonance and details the strong magnetic field dependence of the process.

Findings

Photoassociation loss rate varies by over 10^4 near the Feshbach resonance.

Saturation of the photoassociation rate observed in BEC at high laser intensities.

Frequency shift exhibits an anomalous blue-shift just below the Feshbach resonance.

Abstract

We measure the effect of a magnetic Feshbach resonance (FR) on the rate and light-induced frequency shift of a photoassociation resonance in ultracold $^7$Li. The photoassociation-induced loss rate coefficient, $K_p$, depends strongly on magnetic field, varying by more than a factor of 10$^4$ for fields near the FR. At sufficiently high laser intensities, $K_p$ for a thermal gas decreases with increasing intensity, while saturation is observed for the first time in a Bose-Einstein condensate. The frequency shift is also strongly field-dependent and exhibits an anomalous blue-shift for fields just below the FR.