Robust conversion of singlet spin order in coupled spin-1/2 pairs by adiabatically switched RF-fields

TL;DR

This paper introduces a robust adiabatic RF-field switching technique in NMR to efficiently convert between singlet spin order and magnetization in coupled spin-1/2 pairs, applicable to various coupling regimes.

Contribution

The authors develop a novel adiabatic RF switching method that achieves maximum efficiency in converting singlet order to magnetization and vice versa, applicable to both strongly and weakly coupled spins.

Findings

Method works perfectly for strongly coupled spins

Achieves theoretical maximum conversion efficiency

Useful for long-lived spin hyperpolarization and low-field NMR

Abstract

We propose a robust and highly efficient NMR technique to create singlet spin order from longitudinal spin magnetization in coupled spin-1/2 pairs and to perform backward conversion (singlet order)$\to$magnetization. In this method we exploit adiabatic switching of an RF-field in order to drive transitions between the singlet state and the $T_\pm$ triplet states of a spin pair under study. We demonstrate that the method works perfectly for both strongly and weakly coupled spin pairs, providing a conversion efficiency between the singlet spin order and magnetization, which is equal to the theoretical maximum. We anticipate that the proposed technique is useful for generating long-lived singlet order, for preserving spin hyperpolarization and for assessing singlet spin order in nearly equivalent spin pairs in specially designed molecules and in low-field NMR studies.