Multiple Quantum Coherences Hyperpolarized at Ultra-Low Fields

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Quantum Coherence Phenomena
• Hyperpolarization Techniques

Background:

• Hyperpolarization technologies are crucial for enabling Nuclear Magnetic Resonance (NMR) applications at ultra-low fields (ULF), where signal detection is challenging.
• Conventional NMR faces limitations in sensitivity and spectral resolution at ULF due to negligible chemical shift variations.
• Existing methods often struggle with simultaneous excitation and observation of various spin orders.

Purpose of the Study:

• To present a novel method for simultaneous excitation and observation of multiple quantum coherences (MQCs) in ultra-low field NMR.
• To enhance the degree of freedom in ULF NMR experiments by exploring different orders of MQCs.
• To demonstrate the utility of this approach for ULF NMR spectroscopy.

Main Methods:

• Utilizing heteronuclear correlated spectroscopy (COSY) combined with a phase-cycling scheme for selective MQC observation.
• Employing signal amplification by reversible exchange (SABRE) to generate non-equilibrium spin states and multiple spin orders.
• Detection of MQCs at ULF using a superconducting quantum interference device (SQUID)-based NMR system.

Main Results:

• Simultaneous excitation and observation of homo- and heteronuclear multiple quantum coherences (zero up to third-order) were achieved.
• The developed method allows for selective observation of MQCs of different orders, providing enhanced spectral information.
• Successful detection of these coherences at ULF using a SQUID-based NMR system was demonstrated.

Conclusions:

• The presented method significantly expands the capabilities of ULF NMR by enabling the study of multiple quantum coherences.
• This approach offers a new degree of freedom for ULF NMR experiments, overcoming limitations of negligible chemical shift variations.
• The combination of SABRE, COSY, and SQUID detection provides a powerful platform for advanced ULF NMR applications.