Spinning Molecules Into Reactive States with an Optical Centrifuge

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Professor Amy Mullin of the University of Maryland is supported by the Chemical Structure, Dynamics and Mechanisms Program to carry out studies to elucidate the structure and behavior of molecules in extremely high rotational states in an optical centrifuge. The optical centrifuge is based on combined ultrafast laser pulses that trap molecules and spin them into states with large amounts of angular momentum, in some cases exceeding the chemical bond energy. The behavior of the centrifuged molecules will be interrogated using high-resolution state-resolved transient IR absorption spectroscopy. Project plans are to (1) measure the energy loss dynamics of centrifuged carbon dioxide molecules as they undergo cooling collisions, (2) perform spectroscopic studies of carbon dioxide in the optical centrifuge to discover how large amounts of angular momentum affect the length of chemical bonds and the shape of the molecules, (3) characterize the initial quantum state distribution of molecules excited in the optical centrifuge, (4) explore how magnetic sub-levels are populated when using optical fields to trap molecules, and (5) test new molecules as candidates for optical centrifuge studies.The optical centrifuge is an exciting and powerful new method for preparing molecules in a previously unexplored region, that of very high rotational states. The studies represent a new frontier in chemical dynamics and have the potential to impact many areas of science and technology. The ability to spatially control the rotational motion of molecules opens the door for developing new types of chemistry and gaining new insights into molecular motion, structure and energy at a microscopic energy. High energy molecules are important species in high temperature environments, such as plasmas, combustion and atmospheric chemistry. The fundamental insights to be gained in this research may lead to cleaner, more efficient, and safer applications in these areas. Along with the education of graduate students, this project gives undergraduates and high school teachers important opportunities to participate directly in the state-of-the-art scientific research.