Satellite-transition double cross-polarization HETCOR under fast MAS

Area of Science:

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

Background:

• Proton-detected heteronuclear correlation (HETCOR) is a powerful NMR technique.
• Studying half-integer quadrupolar nuclei often involves challenges with central transition (CT) signals.
• Satellite transitions (STs) and double-quantum satellite transitions (DQSTs) offer complementary information but are difficult to access.

Purpose of the Study:

• To demonstrate efficient double-cross polarization (DCP) for accessing satellite transitions (STs) in proton-detected HETCOR experiments.
• To overcome signal cancellation issues inherent in one-step excitation methods.
• To achieve high-resolution spectra of quadrupolar nuclei, including DQSTs.

Main Methods:

• Implementation of double-cross polarization (DCP) targeting satellite transitions (STs) under fast magic-angle spinning (MAS).
• Utilizing off-resonance radiofrequency (rf) fields selective for STs.
• Applying average Hamiltonian theory to understand the effective rf field dynamics.
• Performing ST and DQST HETCOR experiments on 35Cl nuclei in histidine·HCl·H2O.

Main Results:

• Successful demonstration of efficient DCP HETCOR for STs of half-integer quadrupolar nuclei.
• Elimination of signal cancellation observed in one-step excitation methods.
• Acquisition of ST and DQST HETCOR spectra for 35Cl, providing information beyond standard CT spectra.
• Near isotropic resolution achieved for DQST of spin S=3/2 nuclei.

Conclusions:

• DCP HETCOR is an efficient method for studying STs and DQSTs of quadrupolar nuclei.
• This technique provides valuable complementary information to conventional CT-based NMR spectra.
• The method offers potential for enhanced resolution and detailed structural insights in solid-state NMR.