Dynamic nuclear polarization with simultaneous excitation of electronic and nuclear transitions

TL;DR

This paper introduces a novel method for dynamic nuclear polarization that involves simultaneous excitation of electronic and nuclear transitions, leading to improved efficiency at higher magnetic fields, demonstrated with N@C60 molecules.

Contribution

The study presents a new technique for DNP using simultaneous electronic and nuclear transition excitation, enhancing polarization transfer efficiency at high magnetic fields.

Findings

Higher polarization achieved with continuous-wave microwaves.

Nuclear polarization monitored via hyperfine components.

Nuclear relaxation times are significantly longer than electronic ones.

Abstract

Dynamic nuclear polarization transfers spin polarization from electrons to nuclei. We have achieved this by a new method, simultaneously exciting transitions of electronic and nuclear spins. The efficiency of this technique improves with increasing magnetic field. Experimental results are shown for N@C60 with continuous-wave microwaves, which can be expected to produce even higher polarization than the corresponding pulsed techniques for electron spins greater than 1/2. The degree of nuclear polarization in this case can be easily monitored through the intensities of the well resolved hyperfine components in the EPR spectrum. The nuclear spin-lattice relaxation time is orders of magnitude longer than that of the electrons.