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

摘要

We have performed precision microwave spectroscopy on ultra-cold Rb-87confined in a magnetic trap, both above and below the Bose-condensationtransition. The cold collision shifts for both normal and condensed clouds weremeasured, 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 theimportance of mean-field and velocity-changing collisions in preservingcoherence is discussed.