Contribution Invited Talk
The characteristic of dust in molecular clouds
In the interstellar medium (ISM), amorphous silicates and carbonaceous materials must be the result of grain condensation and growth at low temperatures and densities in molecular clouds. In our laboratory, we have designed experiments to study the cold condensation and processing of silicates and carbon material in the ISM. Molecular precursors that are the results of destructive dust processes in the ISM were produced in the laboratory and deposited on substrates kept at temperatures between 6 and 20 K. We have studied the condensation of refractory siliceous and carbonaceous dust. Our experimental results support the hypothesis that interstellar silicates and carbon are formed by accretion through barrierless reactions. In addition, first results on the co-accretion of carbonaceous and silicate species in ices and the formation of mixed dust will be discussed. After the reformation of dust in molecular clouds, the refractory material is continuously processed by ion bombardment resulting in a ceaseless change of the dust composition and structure.