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This content will become publicly available on February 23, 2017

Title: Magnetic resonance imaging of DNP enhancements in a rotor spinning at the magic angle

Simulations performed on model, static, samples have shown that the microwave power is non-uniformly distributed in the magic angle spinning (MAS) rotor when using conventional dynamic nuclear polarization (DNP) instrumentation. Here, we applied the stray-field magic angle spinning imaging (STRAFI–MAS) experiment to generate a spatial map of the DNP enhancements in a full rotor, which is spun at a low rate in a commercial DNP–MAS NMR system. Notably, we observed that the enhancement factors produced in the center of the rotor can be twice as large as those produced at the top of the rotor. Surprisingly, we observed that the largest enhancement factors are observed along the axis of the rotor as opposed to against its walls, which are most directly irradiated by the microwave beam. We lastly observed that the distribution of enhancement factors can be moderately improved by degassing the sample and increasing the microwave power. The inclusion of dielectric particles greatly amplifies the enhancement factors throughout the rotor. Furthermore, the STRAFI–MAS approach can provide useful guidance for optimizing the access of microwave power to the sample, and thereby lead to further increases in sensitivity of DNP–MAS NMR.
Authors:
 [1] ;  [1] ;  [2]
  1. Ames Lab., Ames, IA (United States)
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
OSTI Identifier:
1254297
Report Number(s):
IS-J--8975
Journal ID: ISSN 1090-7807; PII: S1090780716000446
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Journal of Magnetic Resonance
Additional Journal Information:
Journal Volume: 264; Journal Issue: C; Journal ID: ISSN 1090-7807
Publisher:
Elsevier
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY DNP solid-state NMR; STRAFI–MAS MRI; DNP enhancement