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Title:Nanoscale nuclear spin imaging: Dynamical decoupling and diffraction in a magnetic resonance force microscope
Author(s):Rose, William
Director of Research:Budakian, Raffi
Doctoral Committee Chair(s):Giannetta, Russ
Doctoral Committee Member(s):Dahmen, Karin; Gadway, Bryce
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Optimal control
Abstract:Nuclear magnetic resonance (NMR) has been one of the most powerful scientific tools for medical imaging and chemical structure analysis for decades due to its ability to perform non-destructive three-dimensional imaging combined with the many ways nuclear spins can provide information about their local environment. Recently, techniques to perform NMR on nanoscale spin ensembles have been developed to provide new tools for studying biomolecules and novel materials. Magnetic resonance force microscopy (MRFM), in which spins are coupled to the resonance of a mechanical oscillator, has been used for three-dimensional imaging of 1H spins with resolution below 10 nm. This capability is impressive but not yet sufficient to contribute substantially to a scientific understanding of biomolecules or other materials. Two options for increasing the utility of MRFM are to further improve the imaging sensitivity and resolution, and to find ways to combine it with other powerful analytic methods such as NMR spectroscopy. This work presents analysis of and improvements to many aspects of one powerful MRFM platform. We present fabrication methods for producing silicon nanowires (SiNWs) which are optimized for force sensing, and discussion of the tradeoffs involved. We analyze laser interferometry used to detect the displacement of SiNWs and study the impact of laser wavelength and SiNW dimensions on heating and displacement sensitivity. We then move from improvements to the experimental apparatus to new pulse schemes incorporating optimal control theory, which enable techniques such as dynamical decoupling from solid-state NMR spectroscopy. We use dynamical decoupling sequences to perform line-narrowing by 500 times on 1H spins, which enables one-dimensional imaging with 2 nm resolution. These line-narrowing experiments also demonstrate the potential for incorporating spectroscopic measurements more fully into nanoscale NMR. Finally, making use of novel applications of optical control to adiabatic pulse design, we demonstrate the potential of NMR diffraction to provide sub-angstrom information on periodic samples, which could lead to atomic-scale NMR imaging.
Issue Date:2021-04-19
Rights Information:Copyright 2021 William Rose
Date Available in IDEALS:2021-09-17
Date Deposited:2021-05

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