Research

Molecular Reaction Dynamics Probed Via Pure Rotational Spectroscopy

My students and I have designed, built and tested a unique instrument for probing molecular reaction dynamics via pure rotational spectroscopy. The technique takes advantage of high frequency microwave sources in the millimeter and sub-millimeter wavelength region to probe the products of gas phase reactions.  The ultimate goal of this research is to deduce the molecular electronic states involved in the transition state of a chemical reaction by measuring the speed, direction and internal energy of the products, much the same way an officer attempts to determine the cause of a car accident by studying the wreckage.   Product molecules may be formed in a wide variety of rotational, vibrational, and electronic (rovibronic) states.  Measuring and predicting these distributions is the primary way that physical chemists attempt to understand the nature the transition states of gas phase reactions.  The ultrahigh resolution afforded by the microwave technology has allowed us to probe these product state distributions with unprecedented hyperfine detail.

These sorts of experiments involve a variety of high-tech devices and tools including high powered lasers, oscilloscopes, vacuum chambers and pumps, supersonic molecular beams, as well as microwave sources and liquid helium cooled detectors.  We have performed single molecular beam photodissociation experiments to emulate UV induced reactions implicated in ozone depletion and more recently we have begun crossed molecular beam experiments to study bimolecular reactions of reactive radical species such as excited oxygen (1D) atoms.  We also have a tangentially related project to slow molecular beams using a microchip based Stark decelerator.  We are designing this chip with the ultimate goal of producing ultracold molecules for the study of ultracold chemistry.