The importance of ice in the interstellar medium is indisputable. Gas phase reactions relying on three-body collisions are exceedingly rare in the sparse medium between the stars. On solid surfaces... Show moreThe importance of ice in the interstellar medium is indisputable. Gas phase reactions relying on three-body collisions are exceedingly rare in the sparse medium between the stars. On solid surfaces, atoms and molecules can reside and rove the surface until a reaction takes place. Upon reaction, the released energy is dissipated into the grain, allowing the new species to form. Solid surfaces thus act as sites for chemical processes, that would otherwise be very slow, or not take place at all. This thesis is dedicated to the study of the composition and physical characteristics of interstellar ices using a variety of experimental observational techniques. The overall goal is to shed light on the processes that chemically enrich planet-forming regions. The specific objectives are to characterize morphological changes and molecular composition in interstellar ices, to explore new experimental techniques to study solid state reactions, and to use complex molecules to probe large scale astronomical phenomena. Show less
It has been a long standing problem in astrochemistry to explain how molecules can form in a highly dilute environment as the interstellar medium. In recent years it has become clear that solid... Show moreIt has been a long standing problem in astrochemistry to explain how molecules can form in a highly dilute environment as the interstellar medium. In recent years it has become clear that solid state reactions on icy grains play an important role in the formation of both simple and rather complex molecules. Laboratory based experiments that simulate the UV processing or the impact of H-atoms on interstellar ice analogues are needed in order to investigate the underlying processes. This is the topic of this PhD thesis that mainly summarizes research on SURFRESIDE, one of the ultra-high vacuum setup in the Sackler Laboratory for Astrophysics. It is shown how under fully controlled conditions molecules form when CO and O2 containing ices are bombarded by hydrogen atoms. Surface reaction schemes for methanol, water, carbon dioxide and formic acid formation at low temperatures in space are presented, and it is discussed how species may be chemically linked in space. Show less
The formation of complex organic molecules that consist of more than four atoms in space is one of the main questions in the field of astrochemistry and star formation. Although the exact formation... Show moreThe formation of complex organic molecules that consist of more than four atoms in space is one of the main questions in the field of astrochemistry and star formation. Although the exact formation mechanisms are not yet known, they are expected to form in thin ice layers on the surfaces of small interstellar dust grains through successive addition of H, C, N or O atoms to CO (carbon monoxide). In this thesis the formation of these molecules is studied in two different ways: simulation of interstellar ices analogues in the laboratory and observations of the same molecules after evaporation toward star forming regions. The laboratory experiments are high and ultra high vacuum setups in which ices of e.g. CO, CO2, HCOOH and CH3CHO are frozen out on an inert surface. The spectroscopy and the thermal behavior of pure and layered ices have been studied. Furthermore, the ices have been bombarded with H-atoms to test reactions schemes relevant for astronomical environments. In the second part of this thesis the same molecules have been observed with the single dish submillimeter telescopes the __James Clerk Maxwell Telescope__ at Hawaii and the Institut de Radioastronomie Millim_trique in Spain toward a sample star forming regions as well as with interferometer the SubMillimeter Array at Hawaii toward two sources. The relative abundances of molecules in different star forming regions measured with the single dish telescopes as well as the spatial extent of the emission detected with the interferometer has been used to determine the chemical relations between complex organics that have also been studied in the laboratory. Show less
