Time domain DNP at 1.2 T

We present the results of an experimental pulsed DNP study at 1.2 T (33.5 GHz/51 MHz electron and H-1 Larmor frequencies, respectively). The results include a comparison of constant-amplitude NOVEL (CA-NOVEL), ramped-amplitude NOVEL (RA-NOVEL) and the frequency-swept integrated solid effect (FSISE) experiments all of which were performed at the NOVEL matching condition, omega(1s) = omega(0l), where omega(1s) is the electron Rabi frequency and omega(0l) the proton Larmor frequency. To the best of our knowledge, this is the first pulsed DNP study carried out at field higher than X-band (0.35 T) using the NOVEL condition. A combination of high microwave power (similar to 150 W) and a microwave cavity with a high Q(similar to 500) allowed us to satisfy the NOVEL matching condition. We also observed stretched solid effect ((SE)-E-2) contributions in the Zeeman field profiles when chirped pulses are applied. Furthermore, the high quality factor of the cavity limits the concentration of the radical to similar to 5 mM and generates a hysteresis in the FS-ISE experiments. Nevertheless, we observe very high DNP enhancements that are comparable to the results at X-band. These promising outcomes suggest the importance of further studies at even higher fields that delineate the instrumentation and methods required for time domain DNP. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

This study conducted the first pulsed DNP experiments at 1.2 T field higher than X-band using the NOVEL condition, achieving very high DNP enhancements. These promising outcomes highlight the importance of further studies at even higher fields to delineate the instrumentation and methods required for time domain DNP.