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Title: Exploring the Limits of Overhauser Dynamic Nuclear Polarization (O-DNP) for Portable Magnetic Resonance Detection of Low γ Nuclei

Nuclear magnetic resonance (NMR) spectroscopy in portable, permanent magnet-based spectrometers is primarily limited to nuclei with higher gyromagnetic ratio, γ, such as 1H, 19F, and 31P due to the limited field strength achievable in these systems. Overhauser effect dynamic nuclear polarization (O-DNP), which transfers polarization from an unpaired electron to a nucleus by saturating an electron paramagnetic resonance transition with an oscillating radio frequency magnetic field, B 1e, can increase the polarization of low γ nuclei by hundreds or even thousands, enabling detection in a portable system. We have investigated the potential for O-DNP to enhance signals using (4-amino-2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO hereafter) as a source of unpaired electrons in a homebuilt ultra-low field (ULF) O-DNP-NMR spectrometer. We have found, in general, that larger concentrations of TEMPO are required for effective O-DNP with low γ nuclei, which has a number of important effects. Spin exchange effects cause the EPR lines to overlap and ultimately merge at high concentrations of TEMPO, fundamentally increasing the maximum possible enhancement, while the electron–electron dipolar interaction reduces both longitudinal and transverse relaxation times for the electrons, dramatically increasing the required B 1e strength. The relationship between TEMPO concentration, B 1e magnitude and O-DNP enhancement is quantified, andmore » strategies for achieving these fields are discussed.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-17-28705
Journal ID: ISSN 0937-9347
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Applied Magnetic Resonance
Additional Journal Information:
Journal Volume: 49; Journal Issue: 7; Journal ID: ISSN 0937-9347
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; Atomic and Nuclear Physics; NMR Overhauser DNP ULF
OSTI Identifier:
1463482

Yoder, Jacob Luther, Magnelind, Per Erik, Espy, Michelle A., and Janicke, Michael Timothy. Exploring the Limits of Overhauser Dynamic Nuclear Polarization (O-DNP) for Portable Magnetic Resonance Detection of Low γ Nuclei. United States: N. p., Web. doi:10.1007/s00723-018-1014-1.
Yoder, Jacob Luther, Magnelind, Per Erik, Espy, Michelle A., & Janicke, Michael Timothy. Exploring the Limits of Overhauser Dynamic Nuclear Polarization (O-DNP) for Portable Magnetic Resonance Detection of Low γ Nuclei. United States. doi:10.1007/s00723-018-1014-1.
Yoder, Jacob Luther, Magnelind, Per Erik, Espy, Michelle A., and Janicke, Michael Timothy. 2018. "Exploring the Limits of Overhauser Dynamic Nuclear Polarization (O-DNP) for Portable Magnetic Resonance Detection of Low γ Nuclei". United States. doi:10.1007/s00723-018-1014-1.
@article{osti_1463482,
title = {Exploring the Limits of Overhauser Dynamic Nuclear Polarization (O-DNP) for Portable Magnetic Resonance Detection of Low γ Nuclei},
author = {Yoder, Jacob Luther and Magnelind, Per Erik and Espy, Michelle A. and Janicke, Michael Timothy},
abstractNote = {Nuclear magnetic resonance (NMR) spectroscopy in portable, permanent magnet-based spectrometers is primarily limited to nuclei with higher gyromagnetic ratio, γ, such as 1H, 19F, and 31P due to the limited field strength achievable in these systems. Overhauser effect dynamic nuclear polarization (O-DNP), which transfers polarization from an unpaired electron to a nucleus by saturating an electron paramagnetic resonance transition with an oscillating radio frequency magnetic field, B1e, can increase the polarization of low γ nuclei by hundreds or even thousands, enabling detection in a portable system. We have investigated the potential for O-DNP to enhance signals using (4-amino-2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO hereafter) as a source of unpaired electrons in a homebuilt ultra-low field (ULF) O-DNP-NMR spectrometer. We have found, in general, that larger concentrations of TEMPO are required for effective O-DNP with low γ nuclei, which has a number of important effects. Spin exchange effects cause the EPR lines to overlap and ultimately merge at high concentrations of TEMPO, fundamentally increasing the maximum possible enhancement, while the electron–electron dipolar interaction reduces both longitudinal and transverse relaxation times for the electrons, dramatically increasing the required B1e strength. The relationship between TEMPO concentration, B1e magnitude and O-DNP enhancement is quantified, and strategies for achieving these fields are discussed.},
doi = {10.1007/s00723-018-1014-1},
journal = {Applied Magnetic Resonance},
number = 7,
volume = 49,
place = {United States},
year = {2018},
month = {5}
}