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Double resonance structures for NMR and EPR measurements


NMR spectroscopy is one of the most important methods to elucidate the structure and dynamics of molecules. The sensitivity of the spectrometer is a limiting factor. The present invention increases the signal sensitivity and spectral resolution. The new double resonance structure is suited for a combined NMR/EPR spectrometer for the investigation of liquid samples applying dynamic nuclear polarization (DNP) and/or electron nuclear double resonance (ENDOR) techniques.


There exist double resonance structures for DNP and ENDOR measurements. These structures usually consist of a cylindrical microwave resonator, also called helix resonator, producing a high-frequency magnetic field which is required for the experiments.
However, the disadvantage of the known structures is their limited purpose sample volume. For one, they are limited because of the dimensions of the helix resonator which correlates to the wavelength of the excited microwave. Second, large volumes of liquid, particularly aqueous samples are heated up due to the microwave irradiation.

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The new double-resonant structure consists of a strip resonator which generates high-frequency fields for NMR transitions and a microwave resonator for EPR transitions. Part of the strip resonator acts as a flat mirror and reflects irradiating microwaves quasioptical. The open double-resonant structure offers enough space for measurements of samples with a volume up to 200 nl. The volume is about 10 times larger compared to known helix resonators.
Moreover the flat mirror acts as a sample plate, which can be used as a heat sink due to its good thermal conductivity. This allows investigations of liquid samples with a much larger volume. The arrangement includes a spherical mirror. Through the iris of the mirror microwaves can be fed into the microwave resonator. Simulations show that the new double-resonant structure generates an increased magnetic high-frequency signal. Additionally, a strong and very homogeneous magnetic microwave field within the sample is created. Therefore, the spectrometer provides a high signal sensitivity and high spectral resolution.
In an alternate setup the high-frequency resonator formed from a number of parallel arranged electrically conductive strips. Compared to the use of the single strip resonator the conversion factor is further increased. This provides a higher magnetic field strength and an increased NMR-measuring sensitivity is achieved.


  • Increased signal sensitivity and spectral resolution for DNP and ENDOR.
  • Approx. 10-fold larger sample volume (200 nl) compared to known helix resonators
  • Avoidance of overheating of the samples
  • Faster measurements
  • Easy to implement


DNP experiments

  • structural analysis of biomolecules
  • identification and monitoring of contaminants
  • investigation of dynamic molecular interactions

ENDOR experiments

  • investigation of defects in semiconductors
  • investigation of chirality
  • investigation of fullerenes

Wide application range from medical diagnostics to material science.


The technologies can be licensed or assigned. Moreover, collaborations regarding further development are welcome.

INNOVECTIS Gesellschaft für Innovations-Dienstleistungen mbH

Kirstin Schilling
Altenhöferallee 3
60438 Frankfurt




  • DE 10 2008 017 135 erteilt
  • EP 2 269 045 (DE, GB, FR, CH, SE, NL) erteilt
  • US US 8,570,033 erteilt
  • DE 10 2009 048 636 erteilt
  • EP 2 414 820 (DE, GB, FR, CH, SE, NL) erteilt
  • US 8,823,373 erteilt
  • JP 5 399 551 erteilt


nucelar magnetic resonance, NMR, dynamic nuclear polarisation, DNP, Electron paramagnetic resonance, EPR, Electron nuclear double resonance, ENDOR, resonance structures

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