Astrochemistry: From H₃+ to C₆₀

School Colloquia

Our galaxy’s interstellar medium contains roughly 10⁶ more molecules than the Earth, and over 150 different interstellar molecules have been definitively identified by high resolution spectroscopy. However, our inventory of this vast chemical repository remains very incomplete, and our understanding of the chemical and physical processes that produce and destroy these molecules remains primitive. Our group is engaged in an interdisciplinary program of laboratory experiments and astronomical observations aimed at answering some of the key unsolved questions in “astrochemistry.” In this talk, I will describe how our observations of H₃⁺ (the simplest polyatomic molecule) have revealed the presence of a large flux of low energy cosmic rays in diffuse interstellar clouds. I will also present our laboratory measurements of the most common bimolecular reaction in the universe (H₃⁺ + H₂ -> H₂ + H₃⁺) and the simplest electron recombination process for a polyatomic molecule (H₃⁺ + e- -> products), and discuss how these processes determine the ortho:para ratio of H3+ in these clouds. I will provide an update on our development of two new laboratory techniques for molecular ion spectroscopy - cavity-enhanced velocity modulation spectroscopy (CEVMS) and sensitive, resolved, cooled ion beam spectroscopy (SCRIBES)- which we expect will ultimately enable the astronomical detection of more complex molecular ions. Finally, I will report on our search for the first rotationally-resolved spectrum of C₆₀, the largest and most symmetric molecule to be studied with high-resolution spectroscopy.

For more information contact Prof. Ken Brown (404-385-3124).