Aqueous sample in an EPR cavity: Sensitivity considerations

Yuri E. Nesmelov, Anand Gopinath, David D. Thomas

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14 Scopus citations

Abstract

The radial mode matching (RMM) method has been used to calculate accurately the microwave field distribution of the TE011 mode in a spherical EPR cavity containing a linear aqueous sample, in order to understand in detail the factors affecting sensitivity in EPR measurements at X band. Specific details of the experiment were included in the calculations, such as the cavity geometry, the presence of a quartz dewar, the size of the aqueous sample, and the sample's dielectric properties. From the field distribution, several key physical parameters were calculated, including cavity Q, filling factor, mean microwave magnetic field at the sample, and cavity efficiency parameter Λ. The dependence of EPR signal intensity on sample diameter for a cylindrical aqueous sample was calculated and measured experimentally for non-saturated and half-saturated samples. The optimal aqueous sample diameter was determined for both cases. The impact of sample temperature, conductivity, and cavity Q on sensitivity of EPR is discussed.

Original languageEnglish (US)
Pages (from-to)138-146
Number of pages9
JournalJournal of Magnetic Resonance
Volume167
Issue number1
DOIs
StatePublished - Mar 2004

Bibliographical note

Funding Information:
This work was supported by NIH Grants AR32961 (D.D.T.), AR48961 (Y.N.), and fellowship of University of Minnesota Supercomputing Institute (Y.N.).

Keywords

  • Cavity
  • EPR
  • Field distribution
  • Sensitivity
  • Water

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