Speaker：Prof. Klaus Müller-Dethlefs，Founding Director of The Photon Science Institute and School of Chemistry，The University of Manchester，United Kingdom
Venue：April 26, 2011（Tuesday）10:00
Date：School of Sciences Building C302
Title：A Novel Ultra-cold Rydberg Plasma:from Wigner Crystallisation to a Degenerate Bose Gas?
Abstract：：We produce an ultra-cold, very long lifetime Rydberg plasma by two-photon resonant excitation into the ionization threshold region, via the A-state (NA=0), in the expansion region of a supersonic jet close to the nozzle. Collisions in the jet expansion cool the ions in the plasma to ca. 0.2K thus avoiding disorder heating as in MOT Rydberg plasma experiments. This plasma has a very long lifetime and after ca 310?s, when the plasma hits a 4mm diam. aperture, a dramatic increase in density is observed experimentally just behind this aperture. These observations can be explained by a compression of the plasma, which exhibits the properties of a sponge like material, i.e. a plasma crystal. A possible explanation is the formation of a Wigner crystal. A possible route towards the formation of a degenerate Bose gas of the 14N16O+ cations, that is a molecular Bose-Einstein Condensate will be discussed.