Speaker
Dr
Cornelia Jäger
(Friedrich-Schiller-Universität Jena)
Description
The condensation of carbonaceous and siliceous dust under conditions prevailing in molecular clouds has been experimentally studied. For this purpose, molecular species including refractory elements were deposited on cold substrates. The gaseous precursors of such condensation processes in the ISM are formed by erosion of dust grains in supernova shocks. In the laboratory, we have produced the atomic and molecular precursors by laser evaporation of solid dust analoga. The substrates represent the cold surfaces of surviving cold, circumstellar grains. The precursors were isolated in a cryogenic matrix. Diffusion processes were triggered by a gentle annealing of the icy matrix. The efficient formation of amorphous silicates and carbon at temperatures of about 12 K has been monitored by IR spectroscopy. On the other hand, molecule formation can be triggered by ion bombardment at the interface between ice and solid carbon grains leading to strong grain erosion. Laboratory experiments on the erosion of carbonaceous grains by 200 keV protons showed the formation of CO and CO2 molecules at the expense of solid carbon. The observed erosion restricts the lifetime of the solid carbon material and may influence the formation of more complex molecules in astrophysical environments.
Author
Dr
Cornelia Jäger
(Friedrich-Schiller-Universität Jena)