Measuring Interstellar Reactions of Aromatics by Gas-phase Experiments

Cel

The recent discovery of benzonitrile in a nearby cold molecular cloud (Taurus) marks the first detection of an aromatic species in the interstellar medium by radio astronomy. Benzonitrile provides a key link to benzene, which may be a low-temperature precursor to more complex polycyclic aromatic hydrocarbons (PAHs). Understanding the origin of PAHs will help answer fundamental questions about their role in forming interstellar dust as well as potentially prebiotic molecules—material that may be incorporated into new planetary systems.
Computational models are used to pinpoint individual chemical pathways by inputting kinetic rates of various formation and destruction reactions and aiming to reproduce the molecular abundances determined by radio astronomy. Many of these rates have not been measured in the laboratory, especially at low temperature. The MIRAGE project aims to measure reaction kinetics of functionalized benzenes at temperatures relevant to the cold interstellar medium and use these measurements to understand radio observations of aromatics in Taurus molecular cloud. To do this, we will use a new technique in development at the Université de Rennes 1 that combines chirped-pulse (sub)mm-wave (CPMW) rotational spectroscopy with uniform supersonic flows generated by the CRESU technique. This apparatus (one of only a few in development worldwide) will be used to measure kinetics for reactions of benzene. These data are critical to accurately explain the observed abundance of benzonitrile, as well as predicting the abundances of other aromatic species currently targeted for detection.