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Laboratory Astrochemistry: Instrumentation for characterization and kinetics of low temperature small molecules.


Astrochemists seek to understand the rich chemical presence contained in the observable universe through detection and quantification of astronomical molecules and experimental and theoretical molecular physics. To date, around 270 unique molecules have been detected in the interstellar medium or in circumstellar shells. Chemical models are a tool used to understand the evolution of astronomical environments and they are improved with detections and laboratory studies. Thousands of molecular species and tens of thousands of reactions as well as molecular abundances, reaction rates and physical conditions form a network which models the composition of space over time. The accuracy of a model is dependent on the quality of data and the completeness of the network; imprecise and inaccurate data leads to significant uncertainty in the models. Understanding of the formation of complex organic molecules (COMs, defined as carbon containing species with 6 or more atoms) in cold, dense molecular clouds and prestellar cores has been challenged by recent detections, which highlights some deficiencies of chemical models. This work describes experimental and theoretical work increasing astrochemical knowledge through the study of chemical kinetics at low temperatures and through spectroscopic studies of molecules to facilitate their detection in space. A new instrument combining the CRESU method for producing cold, uniform environments with chirped-pulse Fourier transform microwave spectroscopy and laser induced fluorescence has been constructed to measure rate coefficients and branching ratios of neutral-radical reactions. Additionally, the pure rotational spectra of phenylpropiolonitrile (PhC3N), 1-cyanoadamantane (CNAda), 1-isocyanoadamantane (NCAda), o-dibenzonitrile and m-dibenzonitrile were vi measured in the 75–110 and 120–220 GHz ranges, and the vibrational spectra of PhC3N, CNAda and NCAda measured between 50–3200 cm−1. Finally, a new instrument has been constructed to measure broadband (5 GHz), high resolution (<100 kHz) spectra in the THz region using heterodyne detection of synchrotron radiation mixed with a newly developed molecular laser. The instruments described here expand the tools available to laboratory astrochemists for producing data useful for chemical modeling and facilitating high resolution spectroscopic studies of molecules in support of astronomical detection. The spectroscopic measurements of 5 new molecules demonstrated here also provides high quality data useful for their detection by radio or IR telescopes.

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