Symmetry-based pulsed DNP and EPR sequences

Abstract

Pulsed microwave irradiation provides more versatile control over spin dynamics than continuous-wave (CW) methods. This study adapts symmetry-based dipolar recoupling sequences, which are originally designed for magic angle spinning (MAS) NMR, to exploit electron-nuclear interactions for dynamic nuclear polarization (DNP) and pulsed electron paramagnetic resonance (EPR). Using the trityl radical OX071 at X-band (0.35 tesla), phase-modulated microwave pulses were synchronized with the nuclear Larmor period. Experimental results show effective DNP performance and electron-nuclear distance measurements in EPR, consistent with numerical simulations and theory. This work shows that many MAS NMR pulse sequences can be adapted to static pulsed EPR and DNP with minor modifications. This cross-disciplinary approach provides a versatile platform for designing optimized, application-specific magnetic resonance methodologies across various field strengths, subject to instrumental capabilities.