CAREER: Laser Spectroscopic Investigation of Vibronic Interactions in Free Radicals and Molecular Complexes

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With this CAREER award, the Chemical Structure, Dynamics and Mechanisms (CSDM-A) Program of the Division of Chemistry is funding Professor Jinjun Liu of the University of Louisville to conduct experimental studies aimed at understanding how the vibration and electron motion are coupled in small reactive molecules and in ionic dimers. This coupling of electronic and vibrational degrees of freedom is ubiquitous in photochemical reactions, which are an important class of reactions in atmospheric chemistry and in other venues. Post-doctoral, graduate and undergraduate students working on this project will receive training in laser science, spectroscopy, and the design of experimental apparatus, while working on compelling chemical problems with significant real-world impact. Part of this CAREER program is also focused on a number of education projects, including the revamping of the physical chemistry curriculum and the involvement of underrepresented students in his research program.Professor Jinjun Liu and his research group will use a suite of spectroscopic techniques to study the vibronic interactions in chemical species of significance to atmospheric chemistry, combustion chemistry, and other areas. Species to be studied include alkoxy radicals which will be created in an electric discharge and ion pairs of ionic liquids will be created with a heated nozzle. The methods used to interrogate these molecules include: (1) laser induced fluorescence (LIF); (2) dispersed fluorescence (DF); (3) and cavity ringdown spectroscopy (CRDS). More specifically, the alkoxy radical intermediates will be generated by either pulsed electric discharge or laser photolysis, while ion pairs of ionic liquids, a spectroscopically underexplored family of molecular complexes, will be studied in the gas phase using a heated nozzle. LIF and Ultraviolet-CRDS experiments will be conducted to explore the vibrational energy levels of high-lying electronic states, whereas DF- and mid-Infrared-CRDS techniques will be used to investigate the vibronic structure of the lowest electronic states. Spectroscopic study of isolated ionic liquids is aimed at understanding the Coulombic interaction and hydrogen bonding between ion pairs, determining the conformations of the molecular complexes, and connecting their microscopic structure to physiochemical properties. In particular, it is anticipated that the work on Jahn-Teller and pseudo Jahn-Teller interactions will be of considerable interest to theorists.