Magnetic merging of ultracold atomic gases of $^{85}$Rb and $^{87}$Rb

TL;DR

This paper demonstrates a magnetic merging technique for ultracold $^{85}$Rb and $^{87}$Rb gases, optimizing atom number and minimizing heating, enabling efficient creation of isotopic mixtures for sympathetic cooling.

Contribution

It introduces a detailed magnetic merging method with an optimal trajectory prediction, simplifying the preparation of mixed isotopic ultracold gases for quantum degeneracy.

Findings

Optimal merging trajectory maximizes atom number

Minimal heating achieved during merging

Variable isotopic mixtures created with a single laser setup

Abstract

We report on the magnetic merging of ultracold atomic gases of $^{85}$Rb and $^{87}$Rb by the controlled overlap of two initially spatially-separated magnetic traps. We present a detailed analysis of the combined magnetic field potential as the two traps are brought together which predicts a clear optimum trajectory for the merging. We verify this prediction experimentally using $^{85}$Rb and find that the final atom number in the merged trap is maximised with minimal heating by following the predicted optimum trajectory. Using the magnetic merging approach allows us to create variable ratio isotopic Rb mixtures with a single laser cooling setup by simply storing one isotope in a magnetic trap before jumping the laser frequencies to the transitions necessary to laser cool the second isotope. This offers a simple and cost effective way to achieve suitable starting conditions for sympathetic cooling of $^{85}$Rb by $^{87}$Rb towards quantum degeneracy.