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Research topic

The origin and evolution of the molecular universe starts with the injection of material - much of it in molecular or solid form - by stars in the later stages of their evolution, the processing of this material in the interstellar medium by the prevalent ultraviolet radiation fields, energetic particles, and strong shocks, and ends with the incorporation of this material into newly formed stars and their budding planetary systems. In this way, the chemical processes taking place in the interstellar medium may eventually be inherited by planetary systems. Charting this prebiotic evolution and its relationship to the origin of life on earth and possibly other planetary systems in the universe is a key problem within astrophysics. While the first observations of molecules date back to the earliest parts of the last century, only over the last decade, it has become clear that we actually live in a molecular universe. A variety of observations have shown that surprisingly complex molecules are an important component of the interstellar medium. These include the vibrational signatures of large Polycyclic Aromatic Hydrocarbon molecules (PAHs) which dominate the mid-infrared spectra of galaxies as a whole as well as many objects therein, the electronic fingerprints of a variety of complex molecules (carbon chains, fullerenes, and PAHs) in the form of diffuse absorption bands in the visible spectra of stars, and the rotational transitions of some 150 smaller molecules such as ammonia and water in the microwave spectral range. Molecules have an important influence on the heating and cooling of interstellar gas and, therefore, on the cloud structure of the interstellar medium in galaxies. Molecular clouds are the (only) site of ongoing star formation to a large extent because molecules are efficient gas coolers, thereby diminishing thermal support relative to self-gravity. Moreover, molecules suppress the degree of ionization in these clouds and therefore ``decouple'' the gas from any supporting magnetic fields. Molecules play, thus, a key role in the process of star formation. Hence, molecules are directly interwoven into the fabric of the universe. They are an important component of the universe and play a central role in many key processes that dominate the structure and evolution of galaxies. Understanding the origin and evolution of interstellar molecules is therefore a fundamental goal of modern astrophysics.