RUI: Strong-Field Control of Polyatomic Molecules

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General audience abstract:Ultrashort laser pulses have properties that suggest they might be used to directly influence chemical reactions: the force exerted by the laser field can be comparable to the electric force that holds a molecule together, and the pulse can be turned on and off before the molecule will move significantly. Thus, the precise application of a customized laser pulse to an individual molecule might enable the modification of the molecule in a targeted, desired manner. Stated another way, the laser can be thought of as a new type of reagent that drives a chemical reaction. The development of these laser-based reagents could one day allow chemical synthesis of novel materials and medicines that contribute to the public well-being. Progress toward this long-standing goal has been made, but molecules are complex and dynamic, making it difficult to determine the specific laser characteristics to drive a particular process. This work probes the fundamentals of the interactions between strong laser fields and molecules to improve the understanding needed to design appropriate laser pulses. Doing this work with undergraduate students provides motivation for further scientific education and therefore helps develop a highly-skilled workforce. Undergraduate students from Augustana University carry out this work using the laser facilities of the J.R. Macdonald Laboratory at Kansas State University in collaboration with the researchers there.Technical audience abstract:This work probes bond rearrangement in polyatomic molecules using shaped laser pulses to initiate molecular dynamics and sophisticated detection schemes to measure the reaction products. Bond rearrangement, which occurs in forms such as scrambling, hydrogen migration, and roaming, encompasses several of the steps in any chemical reaction. By applying rapid three-dimensional image-based feedback to the closed-loop control of bond rearrangement, the investigators can determine how well these essential steps in a chemical reaction can be controlled by applying a suitable laser field. In addition, the researchers will increase the data acquisition rate of coincidence-time-of-flight feedback for closed-loop control. In either technique, the highly specific feedback guides the closed-loop search to a well-defined goal. Separating the ionization step from the manipulation of the nuclear wave packet during the rearrangement process using multiple laser pulses makes the examination of the control mechanism more direct. By improving the understanding of how the application of a strong, non-perturbative laser field can affect processes via manipulation of the relative phases of the frequency components in the broad bandwidth pulse, the project examines a widely applicable method of coherent control.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.