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Optimizing symmetry-based recoupling sequences in solid-state NMR by pulse-transient compensation and asynchronous
Johannes Hellwagner1, Kshama Sharma2, Kong Ooi Tan1
1Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland.
The Journal of Chemical Physics
|July 3, 2017
Summary
Solid-state nuclear magnetic resonance (NMR) experiments suffer from pulse imperfections. This study introduces pulse-transient compensation strategies to improve the performance and reproducibility of symmetry-based pulse sequences like R26.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
- Quantum Control and Coherence
Background:
- Pulse imperfections, including transients and radio-frequency field inhomogeneity, significantly degrade performance and reproducibility in solid-state NMR.
- Symmetry-based pulse sequences are susceptible to these imperfections, limiting their effectiveness.
Purpose of the Study:
- To quantitatively analyze the impact of pulse imperfections on symmetry-based pulse sequences.
- To develop and demonstrate strategies for compensating these imperfections to restore transfer efficiency.
- To compare the performance of compensated sequences against established methods.
Main Methods:
- Utilized triple-mode Floquet analysis to theoretically describe symmetry-based dipolar recoupling sequences.
- Calculated first- and second-order effective Hamiltonians using realistic pulse shapes.
- Investigated origins of effective fields: pulse transients, flip angle deviations, and fictitious fields.
- Implemented and compared transient-compensated pulses and asynchronous R26 sequence against the SR26 supercycle.
Main Results:
- Demonstrated that pulse transients, flip angle deviations, and fictitious fields are key sources of error.
- Showcased the superiority of the R26 sequence over the SR26 supercycle when employing pulse-transient compensation.
- Achieved significant reduction in experimental error through theoretical understanding and compensation strategies.
Conclusions:
- Pulse-transient compensation and a thorough theoretical understanding are crucial for optimizing solid-state NMR experiments.
- The R26 sequence, when compensated, offers enhanced performance and reproducibility compared to higher-order error-compensating supercycles like SR26.
- Developed strategies effectively counteract pulse imperfections, restoring full transfer efficiency in NMR experiments.
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