Dynamic nuclear polarization at 700 MHz/460 GHz

Area of Science:

• Magnetic Resonance Spectroscopy
• Physical Chemistry
• Instrumentation Science

Background:

• Dynamic Nuclear Polarization with Nuclear Magnetic Resonance (DNP-NMR) is a powerful technique for enhancing signal sensitivity.
• Previous DNP-NMR experiments were limited to lower magnetic field strengths, restricting achievable resolution and sensitivity.
• Higher field strengths promise significant improvements in spectral resolution and sensitivity for complex molecular systems.

Purpose of the Study:

• To design and implement instrumentation for DNP-NMR at unprecedentedly high field strengths.
• To report the first magic-angle spinning (MAS) DNP-NMR experiments at 700 MHz proton/460 GHz electron frequencies.
• To demonstrate the capability of high-field DNP-NMR for high-resolution spectral analysis.

Main Methods:

• Development of specialized probe technology incorporating a 460 GHz microwave channel.
• Implementation of advanced cryogenics, including a novel heat exchanger and a cryogenic exchange system for efficient sample cooling (≤85 K).
• Integration of gyrotrons and microwave transmission lines for high-power microwave delivery to the sample.

Main Results:

• Successful execution of the first MAS DNP-NMR experiments at 700 MHz/460 GHz (16.4 T).
• Achieved sample temperatures ≤85 K, leading to improved DNP enhancements (initial ε=-40).
• Demonstrated excellent spectral resolution in two-dimensional spectra, even in challenging glassy matrices.

Conclusions:

• The developed instrumentation successfully extends DNP-NMR capabilities to significantly higher field strengths.
• The new system enables continuous cryogenic spinning with reduced liquid nitrogen consumption.
• High-field DNP-NMR offers superior resolution, paving the way for detailed structural studies of complex molecules.