An ultra-cold, molecular Rydberg plasma with exceptionally long lifetime and strongly-coupled properties formed by threshold laser excitation in the expansion region of a supersonic jet

TL;DR

This paper reports the creation of an ultra-cold molecular plasma with a remarkably long lifetime and strongly-coupled properties, achieved through laser excitation in a supersonic jet expansion, with potential implications for plasma physics.

Contribution

It introduces a novel method to generate ultra-cold, long-lived molecular plasma with strongly-coupled ions using threshold laser excitation in a supersonic jet.

Findings

Plasma lifetime of approximately 0.5 ms.

Ion Coulomb coupling parameter estimated between 230 and 820.

Ions maintained at temperatures of 0.2K-0.7K.

Abstract

An ultra-cold molecular plasma with extraordinarily long lifetime (~0.5 ms) is generated under strong collisional cooling conditions in the expansion region of a seeded supersonic jet expansion close to the nozzle. A resonant two-photon one-color laser process excites para-difluorobenzene molecules into the high-n Rydberg threshold region. Disorder heating during plasma formation is quenched by the high collision rate in the expansion, which keeps the ions at the translational jet temperature of 0.2K-0.7K. The Coulomb coupling parameter \Gammai for the ions is expected to be ca. 230-820.