DNP enhanced NMR using a high-power 94 GHz microwave source: a study of the TEMPOL radical in toluene

Eugeny V. Kryukov, Mark E. Newton, Kevin J. Pike, David R. Bolton, Radoslaw M. Kowalczyk, Andrew P. Howes, Mark E. Smith, Ray Dupree*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)

Abstract

DNP enhanced (1)H NMR at 143 MHz in toluene is investigated using an NMR spectrometer coupled with a modified EPR spectrometer operating at 94 GHz and TEMPOL as the polarisation agent. A 100 W microwave amplifier was incorporated into the output stage of the EPR instrument so that high microwave powers could be delivered to the probe in either CW or pulsed mode. The maximum enhancement for the ring protons increases from similar to-16 for a 5 mM TEMPOL solution to similar to-50 for a 20 mM solution at a microwave power of similar to-480 mW. The temperature dependence of the enhancement, the NMR relaxation rates and the ESR spectrum of TEMPOL were also studied in an effort to obtain information on the dynamics of the system.

Original languageEnglish
Pages (from-to)5757-5765
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume12
Issue number22
DOIs
Publication statusPublished - 2010

Keywords

  • DYNAMIC NUCLEAR-POLARIZATION
  • NITROXIDE SPIN LABELS
  • MOLECULAR MOTION
  • RELAXATION
  • RESONANCE
  • LIQUIDS

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