Coupled pairs of nuclear spins-1/2 support one singlet state and three triplet states. Transitions between the singlet state and one of the triplet states may be driven by an oscillating low-frequency magnetic field, in the presence of couplings to a third nuclear spin, and a weak bias magnetic field.This phenomenon allows the generation of strong nuclear hyperpolarization of 13C nuclei, starting from the nuclear singlet polarization of a 1H spin pair, associated with the enriched para spin isomer of hydrogen gas. Hyperpolarization is demonstrated for two molecular system.
@article{arxiv.2107.10542,
title = {Low-Frequency Excitation of Singlet-Triplet Transitions. Application to Nuclear Hyperpolarization},
author = {Laurynas Dagys and Christian Bengs and Malcolm H. Levitt},
journal= {arXiv preprint arXiv:2107.10542},
year = {2021}
}