Integrated, stretched, and adiabatic solid effects

TL;DR

This paper develops a comprehensive theory for dynamic nuclear polarization processes, explaining and comparing the integrated, stretched, and adiabatic solid effects, and demonstrating their efficiencies through experiments.

Contribution

It introduces a unified theory for various solid effects in DNP and predicts the conditions under which each effect is most efficient.

Findings

SSE and ASE can outperform ISE in efficiency.

The theory predicts SSE efficiency increases at higher magnetic fields.

Experimental validation at 9.4 GHz confirms the theoretical predictions.

Abstract

This paper presents a theory describing the dynamic nuclear polarization (DNP) process associated with an arbitrary frequency swept microwave pulse. The theory is utilized to explain the integrated solid effect (ISE) as well as the newly discovered stretched solid effect (SSE) and adiabatic solid effect (ASE). It is verified with experiments performed at 9.4 GHz (0.34 T) on single crystals of naphthalene doped with pentacene-d14. It is shown that SSE and ASE can be more efficient than ISE. Furthermore, the theory predicts that the efficiency of the SSE improves at high magnetic fields, where the EPR linewidth is small compared to the nuclear Larmor frequency. In addition, we show that ISE, SSE, and ASE are based on similar physical principles and we suggest definitions to distinguish among them.