STRW local: Colloquia


The formation of complex organics in dense clouds - sweet results from the laboratory

Date: 29-05-2018
Time: 11:00 h
Author: Ko-Ju Chuang

Large areas of space are filled by molecular clouds that consist of gas and (sub)-micron sized silicate and carbonaceous dust grains that are the remnants of dead stars. When these clouds start gravitationally collapsing, the decreasing temperature and increasing density cause gas particles to start accreting onto dust grain surfaces that act as highly effective cryopumps. This results in layered geometries of partially mixed ices on top of the grains that act as molecule reservoirs and cryogenic catalysts on which both simple and complex molecules form in surface reactions, triggered by impacting atoms, electrons and cosmic rays or irradiation by vacuum UV light. These grains form the material from which celestial bodies –comets and planets and their moons –form. A good understanding of the elementary processes taking place in dark interstellar clouds, therefore, is necessary to understand the chemical inventory of stellar systems, like our own Solar system. This talk focuses on laboratory studies investigating the surface chemistry of CO-rich ices on dust grains at temperatures as low as 10 K. The formation mechanisms of complex organic molecules (COMs) are investigated by non-energetic processes (e.g., hydrogenation) and energetic processes (e.g., photolysis). Moreover, the net transfer of the newly formed hydrogenated species from grain surfaces into the gas phase through non-thermal desorption is investigated to link the detection of COMs in the gas phase to their formation in the solid state.