Solid effect DNP polarization dynamics in a system of many spins

TL;DR

This paper presents a new formalism for modeling solid effect DNP in large spin systems, validated against master equation results, revealing how nuclear polarization depends on spatial arrangements and suggesting radical design improvements.

Contribution

The paper introduces a Monte Carlo-based formalism that enables analysis of larger spin systems in solid effect DNP, extending capabilities beyond previous methods.

Findings

Increasing the distance between nuclei and electrons enhances nuclear polarization.

The formalism accurately matches results from the Liouville von Neumann equation.

Implications for designing radicals with improved nuclear polarization.

Abstract

We discuss the polarization dynamics during solid effect dynamic nuclear polarization (DNP) in a central spin model that consists of an electron surrounded by many nuclei. To this end we use a recently developed formalism and validate first its performance by comparing its predictions to results obtained by solving the Liouville von Neumann master equation. The use of a Monte Carlo method in our formalism makes it possible to significantly increase the number of spins considered in the model system. We then analyse the dependence of the nuclear bulk polarization on the presence of nuclei in the vicinity of the electron and demonstrate that increasing the minimal distance between nuclei and electrons leads to a rise of the nuclear bulk polarization. These observations have implications for the design of radicals that can lead to impoved values of nuclear spin polarization. Furthermore, we discuss the potential to extend our formalism for more complex spin systems such as cross effect DNP.