Measurements of the ion velocity distribution in an ultracold neutral plasma derived from a cold, dense Rydberg gas

TL;DR

This study measures the ion velocity distribution in an ultracold plasma created from a dense Rydberg gas, revealing insights into plasma formation and Rydberg interactions, with experimental results compared to theoretical models.

Contribution

First measurement of ion velocity distribution in ultracold plasma from dense Rydberg gas, highlighting differences from theoretical predictions and analyzing Rydberg blockade effects.

Findings

Measured ion velocity distribution using laser-induced fluorescence.

Observed discrepancies between experimental excitation efficiency and Monte-Carlo calculations.

Found no evidence of spatial ordering despite strong Rydberg blockade interactions.

Abstract

We report measurements of the ion velocity distribution in an ultracold neutral plasma derived from a dense, cold Rydberg gas in a MOT. The Rydberg atoms are excited using a resonant two-step excitation pathway with lasers of 4 ns duration. The plasma forms spontaneously and rapidly. The rms width of the ion velocity distribution is determined by measuring laser-induced fluorescence (LIF) of the ions. The measured excitation efficiency is compared with a Monte-Carlo wavefunction calculation, and significant differences are observed. We discuss the conditions for blockaded Rydberg excitation and the subsequent spatial ordering of Rydberg atom domains. While the blockade interaction is greater than the Rabi frequency in portions of the atomic sample, no evidence for spatial ordering is observed.