RUI: High-Resolution Electronic Spectroscopy of Transition Metal-Containing Free Radicals in the Gas Phase

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This award has been funded by the Chemical Structure, Dynamics, and Mechanisms A Program of the Division of Chemistry. It will support the work of Prof. Thomas D. Varberg and his undergraduate student researchers at Macalester College in St. Paul, Minnesota as they record and analyze the electronic spectra of gas-phase free radicals that contain a transition metal atom. These molecules will be studied using laser-excitation spectroscopy in the visible region, with both pulsed and continuous-wave lasers. Spectral analyses will yield accurate values for the principal molecular constants, including the vibrational, rotational, fine, and hyperfine structures. Such analyses will characterize in some detail the nature of each molecule's electronic states and chemical bonding, as well as provide accurate transition frequencies that are of use to scientists in other fields. The molecules targeted for study include diatomic molecules such as gold sulfide, tantalum hydride, tantalum oxide and hafnium fluoride, and linear polyatomic molecules such as zinc acetylide and copper acetylide. Understanding the structure, bonding and spectroscopy of molecules that contain a transition metal is important for several reasons. For example, chemists have learned how to make small clusters of gold atoms known as colloids and then react these colloids with long-chain organic molecules that terminate in a sulfur atom. The resulting gold nanoparticles are possible building blocks for devices to be used for data storage, ultrafast switching and quantum electronics. This NSF award will support fundamental measurements on the diatomic molecule gold sulfide as a study of the simplest form of the gold-sulfur bond, which lies at the heart of the more complex nanoparticle structures. Furthermore, many industrially useful chemical reactions of organic compounds utilize transition metals to catalyze, or speed up, the formation of the desired product. In these catalyzed reactions, a metal-carbon bond is formed and then later broken in transforming the system from reactant to product. Experiments supported by this NSF award will study some of the simplest metal-carbon bonds found in nature, the results of which will help chemists understand such bonding in larger systems. All of these studies will be carried out by Macalester College undergraduate students, which will introduce these young scientists to modern research in physical chemistry and prepare them for graduate training in chemistry, chemical physics, and engineering.