Electron Temperature Evolution in Expanding Ultracold Neutral Plasmas

TL;DR

This study investigates how electron temperature in ultracold neutral plasmas evolves during free expansion, revealing the transition from cooling-dominated to heating-dominated regimes through experiments and simulations.

Contribution

It introduces a combined experimental and numerical approach to characterize electron temperature dynamics and identifies key processes affecting electron heating in ultracold plasmas.

Findings

Transition from adiabatic cooling to inelastic heating regimes.

Quantification of electron heating contributions from radiative decay and disorder.

Experimental validation of the crossover time scales.

Abstract

We have used the free expansion of ultracold neutral plasmas as a time-resolved probe of electron temperature. A combination of experimental measurements of the ion expansion velocity and numerical simulations characterize the crossover from an elastic-collision regime at low initial Gamma_e, which is dominated by adiabatic cooling of the electrons, to the regime of high Gamma_e in which inelastic processes drastically heat the electrons. We identify the time scales and relative contributions of various processes, and experimentally show the importance of radiative decay and disorder-induced electron heating for the first time in ultracold neutral plasmas.