Pulse sequence design for high field NMR with NV centers in dipolarly coupled samples

TL;DR

This paper introduces a novel pulse sequence protocol for high-field NMR using NV center sensors, enabling the study of dipolarly-coupled samples with improved signal extraction and high spatial resolution.

Contribution

The work presents a new synchronized RF and MW pulse protocol that suppresses dipolar couplings and enhances NMR signal detection at high magnetic fields with NV centers.

Findings

Effective elimination of dipolar couplings in samples.

Enhanced NMR signals at high magnetic fields.

Protocol limited by sample coherence time.

Abstract

Diamond-based quantum sensors have enabled high-resolution NMR spectroscopy at the microscale in scenarios where fast molecular motion averages out dipolar interactions among target nuclei. However, in samples with low-diffusion, ubiquitous dipolar couplings challenge the extraction of relevant spectroscopic information. In this work we present a protocol that enables the scanning of nuclear spins in dipolarly-coupled samples at high magnetic fields with a sensor based on nitrogen vacancy (NV) ensembles. Our protocol is based on the synchronized delivery of radio frequency (RF) and microwave (MW) radiation to eliminate couplings among nuclei in the scanned sample and to efficiently extract target energy-shifts from the sample's magnetization dynamics. In addition, the method is designed to operate at high magnetic fields leading to a larger sample thermal polarization, thus to an increased NMR signal. The precision of our method is ultimately limited by the coherence time of the sample, allowing for accurate identification of relevant energy shifts in solid-state systems.