Seminar dr. Sandra Brünken (Physikalisches Institut, Univ. Köln, Germany) (Lecture)
- Tuesday 24 January 2017Add to my calendar
- from 11:00
dr. Sandra Brünken (Physikalisches Institut, Univ. Köln, Germany)
"Molecular Astrophysics: Spectroscopy and Reactions of Cold Molecular Ions"
Molecular processes govern the evolution of our universe. Molecular emission lines, for instance, provide the dominant cooling mechanism in interstellar clouds, enabling their collapse and thus turning them into the birthplaces of stars. Barrierless reactions starting from rather simple molecular ions are the main drivers of the chemistry in particular in cold regions of space. They lead to an increasing level of chemical complexity, and can be viewed as the first steps in the nucleation process of cosmic dust from which later planets like our own emerge. Furthermore, observations of molecular emission and absorption lines constitute the only diagnostics of physical and chemical conditions in most astronomical environments. Laboratory experiments like those presented in this talk, providing spectroscopic and chemical reactivity data, are crucial to interpret the astronomical observations and to gain insight into macroscopic processes like the dynamics of star formation.
In this talk I will demonstrate how the development of general and sensitive spectroscopic schemes offers unique possibilities for the characterization of molecular ions, such as reactive hydrocarbon cations that play an important role in interstellar carbon chemistry. Experiments are performed on mass-selected ions stored and cooled in a cryogenic ion trap. Their spectra are recorded with unprecedented sensitivity by detecting a change in the ion composition as a function of excitation wavelength, using for example the FELIX free electron lasers as radiation sources. Our recent progress on these so-called action spectroscopic methods expands their application beyond the study of electronic and vibrational excitation processes by enabling to record purely rotational molecular spectra, which are a direct prerequisite for radio-astronomical detections of new species in space as will be demonstrated with selected examples. Cryogenic ion trap instruments are also ideally suited to study the kinetics of neutral-ion reactions under controlled conditions resembling those in space. I will outline how the combination of these unique capabilities with advanced spectroscopic schemes can be used for detailed chemical reactivity studies of the formation and growth processes of complex organic species, with a focus on the ubiquituous polycyclic aromatic hydrocarbons and related molecular ions relevant in the rich but still poorly understood carbon chemistry of the universe. These investigations are experimental tests on fundamental molecular physics and chemistry with a wide application potential in astrophysics related to the most basic questions of star and planet formation, and ultimately the origin of life.
dr. Herma Cuppen