Stuttgart 2012 – scientific programme
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A: Fachverband Atomphysik
A 41: Poster: Ultra-cold plasmas and Rydberg systems
A 41.6: Poster
Thursday, March 15, 2012, 16:30–19:00, Poster.V
Measurement of ion relaxation in strongly coupled plasmas — •Georg Bannasch1, Thomas Pohl1, Jose Castro2, Patrick McQuillen2, and Thomas C. Killian2 — 1Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden — 2Physics & Astronomy Department, Rice University, Houston, USA
Relaxation processes in plasmas are well described within the framework of the Landau-Spitzer theory as long as the plasma is in a weakly coupled state, for which the Debye screening length is larger than the mean interparticle distance. However, these two length scales become comparable as the plasma approaches the strongly coupled regime, leading to a divergence of the Landau-Spitzer rate. Ultracold plasmas, created at the onset of strong correlations, grant experimental access to the parameter regime beyond the validity of the Landau-Spitzer theory.
Here, we present a joint experimental and theoretical study of ion - ion collisions in such an ultracold plasma. Velocity-selective optical pumping combined with fluorescence measurements allows to observe velocity relaxation on relevant timescales. In addition, we present exhaustive molecular dynamics simulations that yield good agreement with the experiment, and, combined with a statistical description in terms of density- and field-fluctuations, allow to characterize the collision rate from the weakly coupled to the strongly coupled regime.