State-selected ion-molecule reactions of relevance to planetary atmospheres and cometary comae

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With this award, the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry is funding Professor Cheuk-Yiu Ng of the University of California-Davis to conduct experimental studies to look at the reactions between molecular ions and neutral molecules. In these experiments, Professor Ng and his group will vary the internal energy of the ion (changing its rotational and vibrational energy) to see how this effects the chemical reactivity. The inclusion of a large number of undergraduates in the Ng laboratory is a notable element of this award. The graduate and undergraduate students working on this project will receive technical training in laser science, optical and vacuum methods, and spectroscopy, preparing them for research careers or entry into the skilled technical workforce.Prof. Cheuk-Yiu Ng and his research group will use high power, narrow-bandwidth lasers to generate short-wavelength radiation in the vacuum ultraviolet (VUV) spectral region. This radiation will be used to produce molecular ions (nitrogen, water, oxygen carbon monoxide and carbon dioxide +1 cations) in specific rovibronic states in a molecular beam. Past work by other scientists has shown profound reactivity differences for molecules with varying amounts of vibrational and rotational energy, but relatively little is known about reactivity differences in molecular ions. The total cross section and branching ratios will be measured for a variety of collision partners, including hydrogen, methanol, methane, ammonia, acetylene, ethylene, propane, diacetylene, hydrogen cyanide and water. These reactions are important in the chemistry of the upper atmospheres of planets as well as in the chemistry of cometary comae.