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Very slow expansion of an ultracold plasma formed in a seeded supersonic molecular beam of NO

TitleVery slow expansion of an ultracold plasma formed in a seeded supersonic molecular beam of NO
Publication TypeJournal Article
Year of Publication2009
AuthorsMorrison, JP, Rennick, CJ, Grant, ER
JournalPhysical Review A
Date PublishedJun
Type of ArticleArticle
ISBN Number1050-2947
Keywords3-BODY RECOMBINATION, COMPOUNDS, ELECTRONS, GASES, laser cooling, molecular beams, molecule-photon collisions, NEUTRAL PLASMAS, NITROGEN, Photoexcitation, PLASMA, plasma collision processes, positive ions, RATES, RYDBERG ATOMS, Rydberg states, STATES, TEMPERATURE, TEMPERATURES, VACUUM, Vlasov equation

The double-resonant laser excitation of nitric oxide, cooled to 1 K in a seeded supersonic molecular beam, yields a gas of approximate to 10(12) molecules per cubic centimeter in a single selected Rydberg state. This population evolves to produce prompt free electrons, and a durable cold plasma of electrons and intact NO+ ions. This plasma travels with the molecular beam through a field-free region to encounter a grid. The atomic weight of the expansion gas controls the beam velocity and hence the flight time from the interaction region to the grid. Monitoring electron production as the plasma traverses this grid measures its longitudinal width as a function of flight time. Comparing these widths to the width of the laser beam that defines the initial size of the illuminated volume allows us to gauge the rate of expansion of the plasma. We find that the plasma created from the evolution of a Rydberg gas of NO expands at a small but measurable rate, and that this rate of expansion accords with the Vlasov equations for an initial electron temperature of T-e approximate to 7 K.

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