Kiel 2011 – scientific programme

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P: Fachverband Plasmaphysik

P 1: Niedertemperaturplasmen / Grundlagen

P 1.4: Talk

Monday, March 28, 2011, 17:25–17:40, HS H

Enhanced metastable densities by recombination into Rydberg states in the argon afterglow — •Yusuf Celik¹, Tsanko Tsankov¹, Dirk Luggenhölscher¹, Uwe Czarnetzki¹, and Mitsutoshi Aramaki² — ¹Institute for Plasma and Atomic Physics, Ruhr-University Bochum — ²Department of Electrical Engineering and Computer Science, Nagoya University, Japan

In the afterglow of low pressure plasmas electrons can be cooled efficiently by “evaporation cooling” to temperatures close to the gas temperature. This enhances recombination in general but especially three-body recombination (e + e + Ar⁺). There, recombination occurs dominantly into Rydberg states. Under our experimental conditions (1 Pa, 10¹¹ cm⁻³, 0.1 eV) the upper quantum state is limited by the ionic micro field (Inglis-Teller). Measurements of the plasma density decay rate agree well with an analytical model. Further, by radiative decay the Rydberg atoms are relaxing either to the ground or the metastable states. Since the plasma density is an order of magnitude higher than the initial metastable density, this can enhance substantially the late metastable density. This can be expected to be of high importance for applications in pulsed plasmas as in HPPMS.