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MATPASS/CPMG: a sensitivity enhanced magic-angle spinning sideband separation experiment for disordered solids.
Ivan Hung1, Trenton Edwards, Sabyasachi Sen
1Center of Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA.
Summary
This study introduces a new nuclear magnetic resonance (NMR) experiment combining Carr-Purcell Meiboom-Gill (CPMG) and magic-angle turning/phase-adjusted sideband separation (MATPASS) for enhanced sensitivity in disordered solids. This method improves sensitivity by an order of magnitude for wide-line NMR spectra.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
- Materials Science
- Physical Chemistry
Background:
- Disordered solids present challenges in NMR due to broad spectral lines exceeding the magic-angle spinning frequency.
- Conventional methods for separating isotropic and anisotropic chemical shifts in such materials often suffer from low sensitivity.
- The Carr-Purcell Meiboom-Gill (CPMG) pulse sequence is known for enhancing signal sensitivity through multiple-echo acquisition.
Purpose of the Study:
- To develop a novel NMR experiment for enhanced sensitivity and isotropic/anisotropic chemical shift separation in disordered solids.
- To combine the benefits of CPMG sensitivity enhancement with magic-angle turning and phase-adjusted sideband separation (MATPASS) techniques.
- To enable accurate measurement of chemical shift anisotropy (CSA) in materials with broad spectral lines.
Main Methods:
- A new experimental protocol, MATPASS/CPMG, was developed, integrating CPMG with magic-angle turning (MAT) and phase-adjusted sideband separation (PASS).
- Time-domain data were acquired using a MAT/CPMG pulse sequence.
- Data processing involved f(1) shearing to obtain the PASS representation, utilizing all CPMG echo signals for increased sensitivity.
Main Results:
- The MATPASS/CPMG protocol demonstrated a sensitivity enhancement of approximately an order of magnitude compared to conventional wide-line NMR.
- The method achieved a √2 higher sensitivity than the conventional PASS technique by incorporating all CPMG echo signals.
- Successful application to a GeSe₄ glass sample showed effective separation of isotropic and anisotropic ⁷⁷Se chemical shifts, even when line widths exceeded the spinning frequency.
Conclusions:
- The developed MATPASS/CPMG experiment significantly enhances sensitivity for wide-line NMR spectra of disordered solids.
- This technique allows for accurate separation of isotropic and anisotropic chemical shifts, facilitating CSA measurements.
- The method is particularly valuable for characterizing disordered solid materials where spectral line widths are large.
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