High-Field Solid-State Dynamic Nuclear Polarization with Paramagnetic Systems Beyond Simple Spin 1/2

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Song-I Han at the University of California-Santa Barbara is working to improve our understanding of solid-state Dynamic Nuclear Polarization (DNP), an important means of boosting the sensitivity of Nuclear Magnetic Resonance (NMR), thereby expanding its reach to a wider scope of chemical systems. NMR is a widely used tool for characterizing the composition and dynamics of chemical systems. It is, for example, the technical basis of Magnetic Resonance Imaging (MRI), an important medical diagnostic tool. Dr. Han and her group are devising new probes and new experimental protocols to substantially improve the resolution and sensitivity of NMR analysis of samples containing species and of properties currently not amenable to NMR analysis. The research offers interdisciplinary training opportunities to graduate students by providing hands-on experience in technology and hardware development. The educational impact is enhanced through a structured undergraduate research program, Hands-On-Spin (hSPIN), engaging undergraduate students in instrument development. Dr. Han's research focusses on development of innovative methods for spin manipulations and novel instrumental capabilities, targeting improved understanding and a wider scope of applicability for high-field solid-state Dynamic Nuclear Polarization (DNP). Specifically, her group is using a novel sensitizer scheme to reveal DNP from high-spin systems that would otherwise be invisible to DNP. In the course of these studies, they are clarifying the mechanism behind the Overhauser effect (OE) in insulating solids, unraveling the competition between electron spin exchange (J) and dipolar couplings (D) in DNP under Magic Angle Spinning (MAS), and improving understanding of the potential and range of hyperfine DNP spectroscopy to measure transition metal – nuclear spin distances. The studies are uncovering new DNP mechanisms and novel experimental approaches to extend DNP to spin systems beyond S=1/2. These aims are enabled by developing innovative instrumental capabilities for concurrent electron (e) and nuclear (n) spin resonance excitation and detection; arbitrary waveform generated (AWG) pulse shaping to achieve coherent and/or spin dynamics-assisted e-n polarization transfer; and two-frequency pump-probe 2D Electron DOuble Resonance (ELDOR), under static and MAS conditions. 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.