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A: Fachverband Atomphysik

A 11: Ultra-cold plasmas and Rydberg systems (joint session A/Q)

A 11.1: Poster

Tuesday, September 21, 2021, 16:30–18:30, P

Ultrafast Electron Cooling in an Ultracold Microplasma — •Mario Großmann, Tobias Kroker, Julian Fiedler, Jette Heyer, Markus Drescher, Klaus Sengstock, Philipp Wessels-Staarmann, and Juliette Simonet — The Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, 22761 Hamburg

We utilize the strong light-field of a focused femtosecond laser pulse to instantaneously and locally ionize a controlled number of atoms within a ⁸⁷Rb Bose-Einstein condensate.
The large atomic densities above 10²⁰ m⁻³ combined with low ion temperatures below 40 mK give rise to an initially strongly coupled plasma with up to a few thousand electrons and ions.
Our experimental setup allows us to tune the density, volume and number of ionized atoms as well as the excess energy after ionization which sets the neutrality of the ultracold plasma.
By directly measuring the kinetic energy of the emerging electrons from a highly charged plasma we observe a cooling of the electronic component from 5250 K to 10 K in less then 500 ns.
The finite particle number permits us to perform exact numerical calculations of the plasma dynamics with long-range Coulomb interactions in excellent agreement with our experimental data. These simulations reveal the picosecond dynamics of each particle as well as the ultrafast energy transfer between the electronic and ionic components of the plasma, bridging the natural time-scales of ultracold neutral plasma and ionized nanoclusters.