Many-body kinetics of dynamic nuclear polarization by the cross effect

TL;DR

This paper develops a theoretical model for the cross effect dynamic nuclear polarization mechanism, enabling detailed simulations of polarization dynamics at the individual spin level to optimize experimental conditions.

Contribution

It introduces a novel theory capturing the three-body incoherent processes driving DNP and allows for large-scale simulations of spin ensembles.

Findings

Simulations reveal the role of three-body processes in polarization build-up.

The model enables optimization of experimental parameters for enhanced DNP efficiency.

First detailed spin-level simulations of cross effect DNP for hundreds of nuclei.

Abstract

Dynamic nuclear polarization (DNP) is an out-of-equilibrium method for generating non-thermal spin polarization which provides large signal enhancements in modern diagnostic methods based on nuclear magnetic resonance. A particular instance is cross effect DNP, which involves the interaction of two coupled electrons with the nuclear spin ensemble. Here we develop a theory for this important DNP mechanism and show that the non-equilibrium nuclear polarization build-up is effectively driven by three-body incoherent Markovian dissipative processes involving simultaneous state changes of two electrons and one nucleus. Our theoretical approach allows for the first time simulations of the polarization dynamics on an individual spin level for ensembles consisting of hundreds of nuclear spins. The insight obtained by these simulations can be used to find optimal experimental conditions for cross effect DNP and to design tailored radical systems that provide optimal DNP efficiency.