Optical Dynamic Nuclear Polarization of 13C Spins in Diamond at a Low Field with Multi-Tone Microwave Irradiation.

Vladimir V Kavtanyuk,Hyun Joon Lee,Sangwon Oh,Keunhong Jeong,Jeong Hyun Shim

doi:10.3390/molecules27051700

Abstract

Majority of dynamic nuclear polarization (DNP) experiments have been requiring helium cryogenics and strong magnetic fields for a high degree of nuclear polarization. In this work, we instead demonstrate an optical hyperpolarization of naturally abundant C nuclei in a diamond crystal at a low magnetic field and the room temperature. It exploits continuous laser irradiation for polarizing electronic spins of nitrogen vacancy centers and microwave irradiation for transferring the electronic polarization to C nuclear spins. We have studied the dependence of C polarization on laser and microwave powers. For the first time, a triplet structure corresponding to the N hyperfine splitting has been observed in the C polarization spectrum. By simultaneously exciting three microwave frequencies at the peaks of the triplet, we have achieved C bulk polarization of 0.113 %, leading to an enhancement of 90,000 over the thermal polarization at 17.6 mT. We believe that the multi-tone irradiation can be extended to further enhance the C polarization at a low magnetic field.

Highlights

Dynamic nuclear polarization (DNP) is a technological breakthrough, which can significantly boost the signal-to-noise ratio in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) [1–7]
Hyperpolarization of 13C nuclear spins in diamond may open up new applications in quantum metrology, e.g., a high-field magnetometer [27,28] and a solid-state nuclear spin gyroscope [29]
Experimental Methods HPHT-grown diamond crystal with natural abundance of 13C nuclear spins is used in all measurements presented in this paper

Summary

Introduction

Dynamic nuclear polarization (DNP) is a technological breakthrough, which can significantly boost the signal-to-noise ratio in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) [1–7]. The high cost of conventional DNP instrumentation, based on helium cryogenics and strong magnetic fields, encourages the development of novel DNP techniques. Optical dynamic nuclear polarization has been demonstrated, in which electronic polarization of negatively charged nitrogen-vacancy (NV) centers is transferred to bulk 13C nuclear spins in diamonds (Figure 1a) [17–25]. Hyperpolarization of 13C nuclear spins in diamond may open up new applications in quantum metrology, e.g., a high-field magnetometer [27,28] and a solid-state nuclear spin gyroscope [29]. Hyperpolarized nanodiamonds have a potential application in molecule-targeted in vivo imaging with the advantage of long spin life times [30–34]

Methods

Results

Conclusion