This thesis is an experimental study of the UV irradiation of the interstellar ice analogues, relevant for the different stages of the star and planet formation sequence. It describes in detail... Show moreThis thesis is an experimental study of the UV irradiation of the interstellar ice analogues, relevant for the different stages of the star and planet formation sequence. It describes in detail photodesorption and photoconversion processes, and as such, contributes to worldwide efforts that aim at understanding how chemistry in space could have contributed to the origin of life on Earth and possibly planets around other stars. Show less
In recent years it has become clear that the space in between the stars, contains a remarkable amount of highly diverse molecules, ranging from simple diatomics to large complex species.... Show moreIn recent years it has become clear that the space in between the stars, contains a remarkable amount of highly diverse molecules, ranging from simple diatomics to large complex species. Astronomical observations and dedicated laboratory experiments show that icy dust grains play a prominent role in the chemical enrichment of matter in space. Exotic solid state reactions taking place for temperatures as low as -260 degree merge small abundant species to larger and larger compounds until species are formed that are considered to be of relevance for life; sugars, fats and precursors of amino acids. Ultimately this material is embedded in matter from which stars and planets form. So, could it be possible, that the ingredients for life form everywhere, in space, following very similar chemical pathways? In this thesis a dedicated laboratory study is described that studies exactly these processes. With a new experimental setup the physical and chemical processes are characterized that are needed to interpret and guide astronomical observations and that yield parameters needed as input in astrochemical models. It is concluded that the chemical complexity in the solid state reaches out much further than assumed so far. Show less
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
