Berlin 2005 – scientific programme

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SYPS: Plasmen in ungewöhnlichen Situationen

SYPS 1: Symposium: Plasmas in unusual situations, Part I: Ultracold plasmas

SYPS 1.2: Invited Talk

Monday, March 7, 2005, 11:00–11:30, HU Audimax

Strong coupling effects in expanding ultracold neutral plasmas — •Thomas Pohl — Max-Planck-Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, D-01187 Dresden

In a number of recent experiments ultracold neutral plasmas have been produced by photoionizing laser-cooled atomic ensembles. The very low initial temperatures suggest that these plasmas have been produced deep within the strongly coupled regime. Furthermore, the relaxation timescales realized in these plasmas indicate that Bogoliubov’s functional hypothesis, frequently used in plasma kinetic theory, is violated in the present case, giving rise to an unusual relaxation behavior.

Based on a recently developed hybrid-molecular-dynamics approach [1], we discuss the expansion dynamics of ultracold plasmas with special emphasis on the strongly coupled ion dynamics. We demonstrate that the present method yields an accurate description of recent measurements [2,3] and allows to address important questions beyond present experimental capabilities.

Furthermore, we show that additional laser cooling during the plasma evolution drastically modifies the expansion dynamics, so that crystallization of the ion component can occur in this nonequilibrium system [4].

[1] T. Pohl, T. Pattard and J.M. Rost, Phys. Rev. A 70, 033416 (2004)

[2] C.E. Simien et al., Phys. Rev. Lett. 92, 143001 (2004)

[3] J.L. Roberts et al., Phys. Rev. Lett. 92, 253003 (2004)

[4] T. Pohl, T. Pattard and J.M. Rost, Phys. Rev. Lett. 92, 155003 (2004)