Invited Talk

Spectroscopic Properties of Carbonaceous Matter from the Laboratory

Cornelia Jäger, Mathias Steglich, Thomas Henning, Friedrich Huisken (Max Planck Institute for Astronomy)

In order to understand the formation pathways, as well as their structural, compositional, and spectral properties in different astrophysical environments, dedicated laboratory experiments combined with structural analyses are necessary. Nanometer- and subnanometer-sized carbonaceous matter was generated by means of gas-phase condensation reactions simulating the formation processes of carbonaceous grains and molecules in astrophysical environments. Two formation pathways with different precursors have been analyzed by studying the by-products and the structure of the final condensates. In a low-temperature (LT) condensation (below 1700 K), polycyclic aromatic hydrocarbons (PAHs) are found to be precursors and building blocks for condensing carbonaceous grains. The laboratory experiments have demonstrated that a big variety of PAHs are produced in LT gas-phase condensation reactions. The molecular building blocks of the grains will be partly destroyed in the interstellar radiation field. The remaining large PAHs eventually contribute to the observed spectral signatures of cosmic carbonaceous matter in the UV/VIS and in the IR range. In a high-temperature condensation, carbon chains, fullerene snatches and fullerenes are precursors for grain formation. Consequently, condensation products in cool and hot astrophysical environments should be different. We are going to show the spectral properties with respect to the formation process and the final structure of the carbonaceous condensate.

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