Collision Assisted Zeeman Cooling with Multiple Types of Atoms

TL;DR

This paper explores Collision Assisted Zeeman Cooling using rubidium isotopes, confirming the theoretical cooling rate and identifying hyperfine-changing collisions as a key limitation, with discussions on potential improvements.

Contribution

It experimentally validates the CAZ cooling rate for 85Rb and 87Rb and characterizes the limiting hyperfine-changing collisions in the process.

Findings

Measured CAZ cooling rate matches analytic predictions

Hyperfine-changing collisions significantly limit cooling efficiency

Potential improvements discussed for enhanced cooling performance

Abstract

Through a combination of spin-exchange collisions in a magnetic field and optical pumping, it is possible to cool a gas of atoms without requiring the loss of atoms from the gas. We investigated this technique, Collision Assisted Zeeman Cooling, using 85Rb and 87Rb. We experimentally confirmed that our measured two isotope CAZ cooling rate agreed with a cooling rate predicted though a simple analytic model. As part of the measured cooling rate, we quantitatively characterized the heating rates associated with our actual implementation of this cooling technique and found hyperfine-changing collisions to be a significant limitation for the 85/87Rb gas mixture. We comment on the prospects for improving the cooling performance beyond that presented in this work.