A robust Freeman-Hill-inspired pulse protocol for ringdown-free T₁ relaxation measurements

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Physical Chemistry
• Materials Science

Background:

• Measuring T1 relaxation times is crucial for understanding molecular dynamics and material properties.
• Standard inversion-recovery sequences require equilibrium signal intensities, complicating measurements.
• Existing methods can be sensitive to experimental imperfections and signal broadening.

Purpose of the Study:

• To introduce a novel, more efficient method for measuring T1 relaxation times.
• To reduce the complexity of data analysis in relaxation time measurements.
• To develop a robust technique suitable for challenging NMR conditions.

Main Methods:

• Developed the Split-Inversion Pulse and Recovery (SIP-R) difference-spectroscopy method.
• Reduced curve-fitting parameters from three to two compared to standard inversion-recovery.
• Utilized a decay-to-zero signal functionality advantageous for numerical optimizations.

Main Results:

• The SIP-R method demonstrates robustness against pulse imperfections, field variations, and acoustic effects.
• It reliably measures T1 relaxation times for inhomogeneously broadened signals up to kilohertz linewidths.
• Successful application in 1H NMR experiments on methane gas under high pressure and in the presence of catalysts.

Conclusions:

• SIP-R is a superior alternative to standard inversion-recovery for T1 relaxation time measurements.
• The method simplifies data analysis and enhances reliability under demanding experimental conditions.
• SIP-R is valuable for in-situ studies, including high-pressure catalysis research.