Evolution from a molecular Rydberg gas to an ultracold plasma in a seeded supersonic expansion of NO

TL;DR

This study demonstrates the spontaneous formation of a cold plasma from Rydberg nitric oxide molecules in a supersonic molecular beam, revealing a transition from molecular Rydberg states to an ultracold plasma.

Contribution

It provides experimental evidence of plasma formation from Rydberg molecules in a controlled molecular beam environment, advancing understanding of plasma evolution at ultracold temperatures.

Findings

Formation of free electrons and cold plasma from Rydberg NO molecules.

High-density Rydberg excitation leads to plasma within a molecular beam.

Observation of plasma stability and longevity in ultracold conditions.

Abstract

We report the spontaneous formation of a plasma from a gas of cold Rydberg molecules. Double-resonant laser excitation promotes nitric oxide, cooled to 1 K in a seeded supersonic molecular beam, to single Rydberg states extending as deep as 80 cm$^{-1}$ below the lowest ionization threshold. The density of excited molecules in the illuminated volume is as high as 1 x 10$^{13}$ cm$^{-3}$. This population evolves to produce prompt free electrons and a durable cold plasma of electrons and intact NO$^{+}$ ions.