• Mutschke, H.
• Posch, Th.
• Andersen, Anja Cetti
• Dorschner, J.
• Jäger, C.

Abstract

The most important task of the laboratory astrophysics group in Jena is the preparation, analytical characterization and spectroscopy of cosmic dust analogs. Since silicates and carbon are the main constituents particular attention is devoted to provide data on realistic analogs of these very grain materials.About 80% of the dust condensing in oxygen-rich evolved stars consist of amorphous silicates which may be considered the precursors of crystalline enstatite and forsterite particles detected by the ISO spectroscopy. We present optical constants of amorphous Mg-silicates with varying Mg/Si ratios in a broad wavelength range. The astrophysical usefulness of those dust analogs was tested by comparison of optically thin model spectra based on dust emissivities derived from ISO-SWS spectra of AGB stars in the range 8--30 microns.In astrophysics the absorption behavior of carbon plays an important role for the visibility of stars and the thermal structure of the interstellar medium. Carbon particles condense in the carbon-rich outflows of evolved stars. The optical properties of amorphous or hydrogenated-amorphous carbon materials can show a great diversity due to their internal structure. The influence of carbon structure on the UV including FUV and FIR spectroscopic behavior was investigated by using a suit of carbonaceous material ranging from strongly disordered to rather graphitized material. Presolar nano-diamonds isolated from primitive meteorites are one of the possibilities to study cosmic material directly in the laboratory. One of the most likely scenarios of diamond formation in space is their direct condensation from stellar outflows. In order to model these outflows it is important to know the absorption and scattering cross sections of the nano-diamonds. We have performed spectroscopic studies on meteoritic nanodiamonds from the Vacuum Ultraviolet to the FIR. This consistent absorption spectrum allowed the derivation of the optical constants. Electron energy loss spectroscopy results are used to continue the data to even shorter wavelengths (20 nm).

Topics

• impedance spectroscopy
• amorphous
• Carbon
• grain
• Oxygen
• electron energy loss spectroscopy