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SFB 591

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SFB 591 » Projekte » B1
 

Title

Volume polymerisation processes in plasmas: Astroanalogues

Project manager

Prof. Dr. Jörg Winter
Institut für Experimentalphysik II
Anwendungsorientierte Plasmaphysik
Ruhr-Universität Bochum

Prof. Dr. Rolf Chini
Astronomisches Institut
Ruhr-Universität Bochum

PD Dr. Johannes Berndt
Institut für Experimentalphysik II
Anwendungsorientierte Plasmaphysik
Ruhr-Universität Bochum

Mitarbeiter »

  Summary
  Goals

Nano-particles play an important role in astrophysics (e.g. interstellar and intergalactic dust clouds) but in medicine too ("Trojan horses" for transport of active substances into the organism), in chemistry (catalysis) and within many other ranges of technology (e.g. production of new materials). Plasmas in reactive gases are successfully used, in order to produce nano-particles with controlled characteristics. For astrophysical questions the optical characteristics of nano-particles and their dependence on size distribution, composition and form are of special interest for a comparison with observations. Such questions are the center of this subproject. The mechanisms that determine particle growth are unknown to a large extent - they are a further central investigation article.

Nano-particle with systematically changed composition (C-H, C-Si-H, C-Si-O-H, etc..) and morphology (e.g. "fluffy particles") shall be produced in RF-plasmas from reactive gases and be examined regarding their formation kinetics, structure and optical characteristics. The physical and chemical variables (gas composition, pressure, power, presence of large quantities of neutral radicals, UV radiation portion) are to be varied systematically. Because of its close relation to astrophysics special attention is dedicated to the optical characteristics in the close infrared range. The question, how the IR-signatures change, if particles are exposed e.g. to a significant flux of atomic hydrogen, is also of importance. Since a short while in situ diagnostics of these particles in plasma with multi-pass fourier-transform-infrared-absorptionspectroscopy (FTIR) and Mie-ellipsometry is possible. This permits it to pursue directly the change of the signatures with progressive growth for the first time. The dynamics of the early precursorphase and its chemical conversion is diagnostically opened by simultaneous use of plasma-ion-mass-spectrometry. The characterisation of the particles is supplemented by ex-situ diagnostics of selected samples.

A goal of this project is the systematic production of nano-particles of different composition and size in reactive RF-stimulated plasmas. Their properties are to be characterized and their signatures are to be compared with observations in astrophysics, that can be led back to very large molecules or particles. Thus the interpretation of the astronomical observations is to be supported. The center of interest are the optical signatures of the produced particles, in particular in the close infrared range. By the usage of efficient, partly new in-situ diagnostics we expect here a clear progress in relation to the present state of research.

A second, equally important goal is the further clearing-up and an improved understanding of the complex growth mechanisms of particles in plasmas. The new diagnostics takes here a key position, whose efforts are supported by accompanied modelling.

 
 
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