Toward the Coherent Control of Large Amplitude Molecular Dynamics

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In this project, funded by the Chemical Structure, Dynamics and Mechanisms Program of the Chemistry Division, Prof. Geoffrey Blake of the California Institute of Technology will conduct a research program that seeks to coherently control the large amplitude molecular dynamics in isolated molecules and hydrogen bonded clusters using sub-picosecond Terahertz (THz) pulses. Specifically, intense (up to MV/cm) THz electric fields will be generated by tilted pulse front generation in lithium niobate crystals and/or plasma filamentation in gaseous media in order to pump the softest intramolecular and intermolecular modes in target systems to high degrees of excitation. The resulting state distributions and internal dynamics will be probed, with complete eigenstate resolution, by chirped pulse-Fourier Transform MicroWave spectroscopy. The first targets are small prebiotic molecules that also serve as molecular models of hydrogen bonding interactions pivotal to the structure and activities of biopolymers, along with hydrogen bonded clusters that illuminate the fundamental interactions that govern the formation of aqueous aerosols in the atmosphere. The pump-probe spectra and time-resolved dynamics will provide the transformational tools that are needed for observations with the next generation of microwave to THz telescopes such as the Atacama Large Millimeter Array, in the exploration of the complex potential energy surfaces of liquids and bioplymers, and in the development of coherent control strategies for the large amplitude motion that operate in even the simplest building blocks of hydrogen bonded assemblies. This research uses new light source and detection technology that allows the weak but very important interactions between hydrogen bonded molecules to be observed with unprecedented resolution. Understanding these interactions is important in many fields; this work focuses on interactions in small prebiotic molecules that are monitored in space and water clusters that are important to understanding the formation and fate of aerosol particles in the atmosphere. This project will be conducted with the assistance of graduate and undergraduate students, including women and members of underrepresented minorities. In addition to these activities, the group headed by Prof. Blake is strongly involved in the Caltech K-12 educational/outreach programs, and is developing new teaching modules in spectroscopy for hands-on science curricula in local classrooms. The support provided here will also make it possible to develop low-cost laboratory instruments and experiments for inquiry-based undergraduate instruction that highlights the strong ties between molecular dynamics and spectroscopy.