Symmetry-based recoupling in double-rotation NMR spectroscopy

Area of Science:

• Magnetic Resonance Spectroscopy
• Quantum Mechanics
• Physical Chemistry

Background:

• Symmetry-based pulse sequences are crucial in nuclear magnetic resonance (NMR) spectroscopy.
• Magic-angle-spinning (MAS) NMR is a standard technique for high-resolution solid-state NMR.
• Extending these techniques to more complex sample rotation schemes is desirable.

Purpose of the Study:

• To extend the theory of symmetry-based pulse sequences (CN(n)(nu) and RN(n)(nu)) to double-rotation NMR.
• To investigate the applicability of these sequences for recoupling homonuclear dipolar interactions and J-couplings.
• To demonstrate the excitation of double-quantum coherences in quadrupolar nuclei using a specific pulse sequence under double-rotation conditions.

Main Methods:

• Theoretical extension of symmetry-based pulse sequences to double-rotation NMR.
• Analysis of transformation properties of homonuclear dipolar interactions and J-couplings.
• Application and synchronization of the R2(2)(1)R2(2)(-1) pulse sequence with outer sample rotation.
• Excitation of double-quantum coherences using central-transition-selective 90-degree pulses.

Main Results:

• The theory of CN(n)(nu) and RN(n)(nu) pulse sequences is successfully extended to double-rotation NMR.
• The R2(2)(1)R2(2)(-1) pulse sequence is shown to be effective for homonuclear dipolar recoupling in double-rotation NMR.
• Double-quantum coherences were successfully excited in homonuclear spin systems of (23)Na and (27)Al nuclei.

Conclusions:

• Double-rotation NMR provides a new platform for symmetry-based pulse sequence applications.
• The adapted R2(2)(1)R2(2)(-1) pulse sequence is a valuable tool for recoupling interactions in quadrupolar nuclei under double-rotation.
• This work facilitates advanced NMR studies of quadrupolar nuclei in solid-state systems.