Optically induced dynamic nuclear spin polarisation in diamond

TL;DR

This paper demonstrates a method to achieve room-temperature hyperpolarisation of 13 C nuclear spins in diamond using optical pumping of NV centres, enhancing MRI contrast without cryogenic conditions.

Contribution

It introduces an efficient, robust scheme for optically induced nuclear spin polarisation in diamond at room temperature and low magnetic fields, overcoming previous cryogenic limitations.

Findings

Achieved room-temperature 13 C hyperpolarisation in diamond.

Demonstrated optical pumping of NV centres transfers polarisation to nuclear spins.

Developed protocols robust against magnetic field misalignment.

Abstract

The sensitivity of Magnetic Resonance Imaging (MRI) depends strongly on nuclear spin polarisation and, motivated by this observation, dynamical nuclear spin polarisation has recently been applied to enhance MRI protocols (Kurhanewicz, J., et al., Neoplasia 13, 81 (2011)). Nuclear spins associated with the 13 C carbon isotope (nuclear spin I = 1/2) in diamond possess uniquely long spin lattice relaxation times (Reynhardt, E.C. and G.L. High, Prog. in Nuc. Mag. Res. Sp. 38, 37 (2011)) If they are present in diamond nanocrystals, especially when strongly polarised, they form a promising contrast agent for MRI. Current schemes for achieving nuclear polarisation, however, require cryogenic temperatures. Here we demonstrate an efficient scheme that realises optically induced 13 C nuclear spin hyperpolarisation in diamond at room temperature and low ambient magnetic field. Optical pumping of a Nitrogen-Vacancy (NV) centre creates a continuously renewable electron spin polarisation which can be transferred to surrounding 13 C nuclear spins. Importantly for future applications we also realise polarisation protocols that are robust against an unknown misalignment between magnetic field and crystal axis.