We present the first DNP MAS experiments using 0.7 mm rotors, allowing us to reach spinning frequencies of 65 kHz at 100 K and 21.1 T (900 MHz), the highest magnetic field available for DNP today.(1)

We show that the mixed radical HyTEK2 allows us to reach DNP enhancements as high as 200 at a MAS rate of 65 kHz, and the carbon-centered radical BDPA in an ortho-terphenyl glass yields an enhancement of 106. For the two systems, we observe the 1H DNP enhancements increasing with increasing MAS frequency, this behaviour has been interpretated using a spin diffusion model.

Faster MAS spinning frequencies enable exceptional 1H resolution in MAS DNP and stimulate the use of 1H detected spectra. We obtained resolved DNP enhanced 1H detected 1H−13C and 1H−15N correlation spectra of microcrystalline histidine·HCl·H2O.

(1) P. Berruyer, S. Björgvinsdóttir, A. Bertarello, G. Stevanato, Y. Rao, G. Karthikeyan, G. Casano, O. Ouari, M. Lelli, C: Reiter, F. Engelke, L. Emsley, Dynamic Nuclear Polarization Enhancement of 200 at 21.15 T Enabled by 65 kHz Magic Angle Spinning. J. Phys. Chem. Lett. 11, 8386-8391 (2020).