Hannover 2020 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 21: Ultracold plasmas and Rydberg systems I (joint session Q/A)
A 21.5: Vortrag
Mittwoch, 11. März 2020, 15:00–15:15, f342
Ultrafast electron cooling in an expanding ultracold plasma — •Tobias Kroker1,2, Mario Neundorf1,2, Klaus Sengstock1,2, Markus Drescher1,2, Philipp Wessels1,2, and Juliette Simonet1,2 — 1Zentrum für Optische Quantentechnologien (ZOQ), Luruper Chaussee 149, 22761 Hamburg — 2The Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, 22761 Hamburg
Local photoionization of a Bose-Einstein condensate with a femtosecond laser pulse provides access to an unprecedented regime of ultracold plasma. The accessible charge carrier density of 2·1014 cm−3 enables the creation of micrometer-sized, strongly coupled plasma with an initial ion coupling parameter of Γ = 4800.
We create a tunable number of up to a few thousand charged particles by strong-field ionization of 87Rb with an electron excess energy of 0.68 eV. Our dedicated experimental setup allows the measurement of the electronic kinetic energy distribution with meV resolution. We report on the direct observation of electron cooling from 5000 K to about 1 K in a few hundred nanoseconds.
The finite plasma size allows for charged particle tracing of the underlying plasma dynamics including mutual Coulomb coupling. The simulations are in excellent agreement with the measurements and provide access to the dynamics on sub-nanosecond timescales. We observe an ultrafast energy transfer of 50% of the excess energy from the electronic onto the ionic component within the first ten picoseconds.