Astrophysical Laboratory / Astromineralogy

Current Fields of Research
  • Solid and molecular carbonaceous matter :
    Cosmic carbonaceous matter may have very different structures and properties, reaching from large molecules, small clusters, fullerenes and nanodiamonds to big soot grains. We are highly interested in the questions what structures may form at circumstellar places and how they evolve in the interstellar medium. To help answering these questions, we perform condensation experiments of amorphous carbon ("soot") grains using a number of laser-based sources in combination with in-situ infrared and ultraviolet spectroscopy, also in the form of matrix-isolation spectroscopy. Additionally, the condensates are analysed by Raman and EEL spectroscopy as well as by high-resolution electron microscopy. In a new project, we investigate the molecular components of the condensates by HPLC. Moreover, we started to investigate structural changes under UV irradiation. In this project we collaborate with the group of Friedrich Huisken at IFK Jena. It is supported by the DFG.
    (Cornelia Jäger, Kamel Gadallah, Harald Mutschke, Collaboration: F. Huisken, IFK/MPIA, M. Schnaiter - IMK Karlsruhe)

  • Infrared spectroscopy of free-flying particles :
    Spectra of the infrared dust emission are nowadays widely used to determine the mineralogy and the size of dust particles in disks and stellar outflows and, thereby, to constrain the evolutionary state of these objects. However, the analysis of these data is affected by the uncertainty of the dust spectra used for comparison, which are usually based on light scattering models and depend on the assumed grain shape. Directly measured laboratory absorption spectra suffer from the drawback that particles are usually embedded into a solid carrier material such as KBr for the measurements. In our new experiment we avoid the influence of such a strongly polarizable matrix by dispersing the particles into a gaseous carrier and measuring the transmission spectra through such an aerosol. Shape and size of the particles are subsequently analysed by REM after deposition onto a nanopore filter directly from the aerosol. We create an internet database of the aerosol spectra and we additionally work on improved theoretical models based on our measured spectra. This project continues or previous theoretical (Andersen et al. 2006) and experimental (Clément et al. 2003) studies on morphological influences on IR resonance band profiles such as of that silicon carbide. It is supported by the DFG.
    (Akemi Tamanai, Harald Mutschke, S. Krivov, Collaboration: Anja C. Andersen - NORDITA Copenhagen, Michiel Min - Univ. Amsterdam)

  • Spectroscopy of silicates at extreme wavelengths and low temperatures :
    Silicates are probably the most abundant cosmic dust materials. The mineralogy of the silicate dust and its spectroscopic properties are our most traditional and still very important subject. Since astronomical infrared spectroscopy has proven in the last years, that cosmic silicates occur both in amorphous and crystalline states, we deal with silicates in both states and with transformation processes between them. So we produce amorphous siliactes by melting, laser ablation, and the sol-gel process, anneal amorphous stuff by temperature treatment, and amorphize crystals by ion irradiation. The products are analyzed by spectroscopy in the wavelength range from 0.12 to 2000 micron. Currently, we focus on the extreme wavelengths such as the vacuum UV (Diploma S. Hummel 2006) and the far-infrared and sub-mm range. For the latter, we are especially interested in the temperature dependence of the dust bands and the continuum sub-mm opacity (Boudet et al. 2005, Koike et al. 2006). The data obtained will help in the interpretation of future observations with Herschel and ALMA.
    (Simon Zeidler, Harald Mutschke, Cornelia Jäger, Collaboration: Claude Meny - CESR Toulouse, Chiyoe Koike - Kyoto Pharm. Univ., Thomas Posch - Univ. Wien)

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Last modified: H. Mutschke, March 2008