Zero- to ultralow-field nuclear magnetic resonance

Area of Science:

• Nuclear Magnetic Resonance Spectroscopy
• Quantum Sensing
• Spectroscopic Analysis

Background:

• Zero and ultralow-field nuclear magnetic resonance (ZULF NMR) operates at magnetic fields where spin-spin interactions dominate over Zeeman interactions.
• This modality utilizes external fields of microtesla strength or below, significantly weaker than Earth's magnetic field.
• ZULF NMR enables the measurement of spin-spin couplings and relaxation rates for chemical identification and analysis.

Purpose of the Study:

• To review the principles and capabilities of ZULF NMR spectroscopy.
• To highlight the advantages of ZULF NMR, including low cost, portability, and high-resolution analysis.
• To discuss recent advancements and future research directions in ZULF NMR.

Main Methods:

• Exploiting nuclear spin Hamiltonian terms suppressed in high-field NMR due to the absence of strong external field symmetry.
• Utilizing d.c. magnetic field pulses for nuclear spin manipulation at audio-band Larmor frequencies.
• Employing highly sensitive magnetometers for signal detection.

Main Results:

• ZULF NMR provides nondestructive chemical identification and fragment analysis.
• Enables novel experiments and applications, including dark matter searches and hyperpolarized contrast agent preparation.
• Achieves high-resolution spectroscopy, even with conductive materials and heterogeneous samples, overcoming limitations of high-field NMR.

Conclusions:

• ZULF NMR is becoming more accessible due to improved magnetometer sensitivity, commercial availability, and hyperpolarization methods.
• The technique offers practical advantages like low cost, simplicity, and portability.
• ZULF NMR presents a promising avenue for future research across various scientific disciplines.