2H NMR pure-quadrupole spectra for paramagnetic solids.

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
• Paramagnetic Materials Characterization
• Molecular Dynamics

Background:

• Deuterium (2H) NMR is valuable for studying molecular dynamics in solids.
• Analyzing paramagnetic solids with 2H NMR is challenging due to spectral complexities.
• Pure-quadrupole spectroscopy simplifies spectral analysis by focusing on the quadrupole interaction.

Purpose of the Study:

• To develop a simple two-dimensional (2D) NMR method for obtaining pure-quadrupole spectra of deuterium (2H) in paramagnetic solids.
• To demonstrate the method's ability to simplify spectral analysis by decoupling paramagnetic shifts.
• To apply the technique for investigating molecular dynamics through temperature-dependent spectral analysis.

Main Methods:

• Implementation of a modified quadrupole-echo sequence with asymmetric pulse spacings.
• Insertion of 180° pulses within the quadrupole-echo sequence.
• Asymmetric incrementing of pulse spacings to isolate the quadrupole interaction in the indirect dimension.
• Simulation of projected spectra using the quadrupole-echo sequence, neglecting paramagnetic shift effects under strong radio-frequency pulses.

Main Results:

• Successful acquisition of 2D (2)H NMR pure-quadrupole spectra for paramagnetic solids.
• Demonstration that the projected spectrum can be simulated without considering paramagnetic shifts when using strong radio-frequency pulses.
• Validation of the method for studying molecular dynamics via temperature-dependent (2)H NMR spectral measurements and simulations.

Conclusions:

• The developed 2D NMR method offers a straightforward approach to obtaining pure-quadrupole spectra of (2)H in paramagnetic solids.
• This technique effectively simplifies spectral interpretation by mitigating the influence of paramagnetic shifts.
• The method is a valuable tool for probing molecular dynamics in complex paramagnetic systems.