Multiple-rotor-cycle 2D PASS experiments with applications to (207)Pb NMR spectroscopy

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
• Materials Science

Background:

• Magic-angle spinning (MAS) NMR spectra often suffer from overlapping spinning sidebands, complicating analysis.
• The standard two-dimensional phase-adjusted spinning sidebands (2D PASS) experiment is effective but limited to lower MAS speeds.
• High chemical shift anisotropy, common in nuclei like 207Pb, exacerbates sideband complexity, necessitating higher MAS speeds.

Purpose of the Study:

• To adapt the 2D PASS technique for high-speed MAS conditions.
• To enable the simplification of NMR spectra for nuclei with large chemical shift anisotropy, such as 207Pb.
• To reduce experimental time by optimizing the 2D PASS sequence for higher spinning speeds.

Main Methods:

• Implementation of multiple-rotor-cycle 2D PASS pulse sequences to avoid pulse overlap at high MAS speeds.
• Development of a version incorporating composite pulses for artifact suppression.
• Application and demonstration of the sequences on 207Pb samples, including lead zirconate.

Main Results:

• Successfully implemented 2D PASS sequences compatible with high-speed MAS (8-12 kHz).
• Demonstrated effective separation of spinning sidebands for 207Pb, yielding simplified isotropic spectra.
• Showcased artifact suppression using composite pulses in the modified sequences.

Conclusions:

• The developed multiple-rotor-cycle 2D PASS sequences are suitable for high-speed MAS NMR.
• These advanced sequences significantly improve spectral simplification for challenging nuclei like 207Pb.
• The technique provides a valuable tool for analyzing complex solid-state materials.