Effect of cold collisions on spin coherence and resonance shifts in a magnetically trapped ultra-cold gas

TL;DR

This paper investigates how cold collisions affect spin coherence and resonance shifts in magnetically trapped ultra-cold Rb-87 gases, providing precise measurements above and below Bose-Einstein condensation.

Contribution

It offers new measurements of cold collision shifts and clarifies intra- and inter-state density correlations in ultra-cold gases, including the role of collisions in coherence preservation.

Findings

Measured cold collision shifts for normal and condensed clouds

Determined intra- and inter-state density correlations

Analyzed the impact of collisions on coherence

Abstract

We have performed precision microwave spectroscopy on ultra-cold Rb-87 confined in a magnetic trap, both above and below the Bose-condensation transition. The cold collision shifts for both normal and condensed clouds were measured, which allowed the intra- and inter-state density correlations (characterized by sometimes controversial "factors of two") to be determined. Additionally, temporal coherence of the normal cloud was studied, and the importance of mean-field and velocity-changing collisions in preserving coherence is discussed.