Sympathetic cooling and collisional properties of a Rb-Cs mixture

TL;DR

This paper investigates the collisional interactions and sympathetic cooling of a Rb-Cs atomic mixture at microkelvin temperatures, providing key scattering parameters and discussing prospects for Bose-Einstein condensation.

Contribution

It presents the first measurement of the inter-species collisional cross-section and s-wave scattering length for Rb-Cs in a magnetic trap, advancing understanding of mixed atomic gases.

Findings

Achieved sympathetic cooling of Cs to a few microkelvin.

Measured inter-species collisional cross-section and scattering length.

Discussed potential for Bose-Einstein condensation of Cs.

Abstract

We report on measurements of the collisional properties of a mixture of $^{133}$Cs and $^{87}$Rb atoms in a magnetic trap at $\mu\mathrm{K}$ temperatures. By selectively evaporating the Rb atoms using a radio-frequency field, we achieved sympathetic cooling of Cs down to a few $\mu\mathrm{K}$. The inter-species collisional cross-section was determined through rethermalization measurements, leading to an estimate of $a_s=595 a_0$ for the s-wave scattering length for Rb in the $|F=2, m_F=2>$ and Cs in the $|F=4, m_F=4>$ magnetic states. We briefly speculate on the prospects for reaching Bose-Einstein condensation of Cs inside a magnetic trap through sympathetic cooling.