Hannover 2013 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 40: Poster: Ultra-cold plasmas and Rydberg systems (with Q)
A 40.9: Poster
Donnerstag, 21. März 2013, 16:00–18:30, Empore Lichthof
Measurement of ion - ion collisions in strongly coupled plasmas — •Georg Bannasch1, Thomas Pohl1, Jose Castro2, Patrick McQuillen2, and Thomas Killian2 — 1Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden — 2Physics & Astronomy Department, Rice University, Houston, USA
Relaxation processes in weakly coupled plasmas are well described within the framework of the famous Spitzer theory [1]. As the theory relies on a Debye screening length λD that is much larger than the mean interparticle distance a, the resulting relaxation rates diverge in the strongly coupled domain, where the two length scales can become comparable. Here, we present a joint experimental theoretical study of ion - ion collisions in an ultracold plasma, created at the onset of strong plasma coupling, beyond the validity of the Spitzer theory. Velocity-selective optical pumping combined with fluorescence measurements permits to observe the dynamics of velocity relaxation [2]. We find excellent agreement between measured rates and theoretical results obtained from molecular dynamics simulations as well as from generalized kinetic theory. The presented framework permits direct access to the velocity dependence of the relaxation rate.
[1] Jr. L. Spitzer. Physics of Fully Ionized Gases. Wiley, New York, 1962
[2] G. Bannasch, J. Castro, P. McQuillen, T. Pohl, and T. C. Killian, Phys. Rev. Lett. 109, 185008 (2012)