Overhauser effects in insulating solids
Author(s)
Caporini, M. A.; Mentink-Vigier, F.; Rosay, M.; Maas, W. E.; Baldus, M.; Vega, S.; Corzilius, Bjorn; Walish, Joseph John; Swager, Timothy M; Griffin, Robert Guy; Can, Thach V; ... Show more Show less![Thumbnail](/bitstream/handle/1721.1/109520/Griffin_Overhauser%20effects.pdf.jpg?sequence=4&isAllowed=y)
DownloadGriffin_Overhauser effects.pdf (510.9Kb)
PUBLISHER_POLICY
Publisher Policy
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Terms of use
Metadata
Show full item recordAbstract
We report magic angle spinning, dynamic nuclear polarization (DNP) experiments at magnetic fields of 9.4 T, 14.1 T, and 18.8 T using the narrow line polarizing agents 1,3-bisdiphenylene-2-phenylallyl (BDPA) dispersed in polystyrene, and sulfonated-BDPA (SA-BDPA) and trityl OX063 in glassy glycerol/water matrices. The 1H DNP enhancement field profiles of the BDPA radicals exhibit a significant DNP Overhauser effect (OE) as well as a solid effect (SE) despite the fact that these samples are insulating solids. In contrast, trityl exhibits only a SE enhancement. Data suggest that the appearance of the OE is due to rather strong electron-nuclear hyperfine couplings present in BDPA and SA-BDPA, which are absent in trityl and perdeuterated BDPA (d21-BDPA). In addition, and in contrast to other DNP mechanisms such as the solid effect or cross effect, the experimental data suggest that the OE in non-conducting solids scales favorably with magnetic field, increasing in magnitude in going from 5 T, to 9.4 T, to 14.1 T, and to 18.8 T. Simulations using a model two spin system consisting of an electron hyperfine coupled to a 1H reproduce the essential features of the field profiles and indicate that the OE in these samples originates from the zero and double quantum cross relaxation induced by fluctuating hyperfine interactions between the intramolecular delocalized unpaired electrons and their neighboring nuclei, and that the size of these hyperfine couplings is crucial to the magnitude of the enhancements. Microwave power dependent studies show that the OE saturates at considerably lower power levels than the solid effect in the same samples. Our results provide new insights into the mechanism of the Overhauser effect, and also provide a new approach to perform DNP experiments in chemical, biophysical, and physical systems at high magnetic fields.
Date issued
2014-08Department
Massachusetts Institute of Technology. Department of Chemistry; Francis Bitter Magnet Laboratory (Massachusetts Institute of Technology)Journal
Journal of Chemical Physics
Publisher
American Institute of Physics (AIP)
Citation
Can, T. V., M. A. Caporini, F. Mentink-Vigier, B. Corzilius, J. J. Walish, M. Rosay, W. E. Maas, M. Baldus, S. Vega, T. M. Swager, and R. G. Griffin. "Overhauser effects in insulating solids." Journal of Chemical Physics 141, 064202 (2014). © 2014 AIP Publishing LLC.
Version: Final published version
ISSN
0021-9606
1089-7690