Erlangen 2022 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 56: Ultra-cold plasmas and Rydberg systems (joint session A/Q)

Q 56.4: Talk

Thursday, March 17, 2022, 14:45–15:00, A-H1

From Highly Charged to Neutral Microplasma — •Mario Großmann, 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

By combining an ultracold quantum gas of ⁸⁷Rb with strong-field ionization in femtosecond laser pulses, we investigate the dynamics of highly charged to neutral microplasmas.
Our experimental setup enables us to detect ions and electrons separately and resolve their kinetic energies.
We locally ionize an ultracold target with densities of up to 10²⁰m⁻³ within a micrometer sized focus. This allows creating initially strongly coupled plasmas with ion temperatures below 40 mK and a few hundred to thousand charged particles.
The excess energy of the electrons can be tuned via the wavelength of the ionizing laser pulse resulting in initial electron temperatures from 5800 K to 65 K. This directly impacts the neutrality of the plasma:
High excess energies yield a highly charged plasma with rapid electron cooling whereas low excess energies trigger a neutral plasma with greatly increased lifetimes. Below the ionization threshold we observe ultrafast excitation of Rydberg states.
The small number of particles permits us to compare our results to molecular dynamics simulations that grant access to the non-equilibrium plasma dynamics on picosecond timescales.