Using Three-Body Recombination to Extract Electron Temperatures of Ultracold Plasmas

TL;DR

This paper demonstrates how three-body recombination rates can be used to measure electron temperatures in ultracold plasmas, revealing ongoing cooling below 1 Kelvin.

Contribution

It introduces a microwave-ionization technique to detect recombination-created Rydberg atoms for temperature extraction in ultracold plasmas.

Findings

Measured recombination rates agree with theory for weakly-coupled plasmas.

Electron temperatures continue to decrease below 1 K during plasma evolution.

Method provides a new way to probe ultracold plasma temperatures.

Abstract

Three-body recombination, an important collisional process in plasmas, increases dramatically at low electron temperatures, with an accepted scaling of T_e^-9/2. We measure three-body recombination in an ultracold neutral xenon plasma by detecting recombination-created Rydberg atoms using a microwave-ionization technique. With the accepted theory (expected to be applicable for weakly-coupled plasmas) and our measured rates we extract the plasma temperatures, which are in reasonable agreement with previous measurements early in the plasma lifetime. The resulting electron temperatures indicate that the plasma continues to cool to temperatures below 1 K.