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Asynchronous symmetry-based sequences for homonuclear dipolar recoupling in solid-state nuclear magnetic resonance
Kong Ooi Tan1, M Rajeswari2, P K Madhu2
1Laboratory of Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zürich, Switzerland.
The Journal of Chemical Physics
|February 16, 2015
Summary
A new theoretical framework using triple-mode Floquet theory analyzes asynchronous recoupling sequences. This method enhances performance for specific spin pairs, outperforming rotor-synchronized sequences in certain conditions.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy
- Quantum dynamics and control
Background:
- Symmetry-based pulse sequences are crucial for recoupling interactions in NMR.
- Rotor-synchronized sequences are common but have limitations, especially with large chemical-shift anisotropy.
- Asynchronous sequences offer potential advantages but require robust theoretical frameworks for analysis.
Purpose of the Study:
- To develop a theoretical framework for analyzing asynchronous recoupling sequences not synchronized to the rotor.
- To investigate the properties and performance of a novel homonuclear double-quantum recoupling sequence.
- To compare the efficiency of the new asynchronous sequence against its rotor-synchronized counterpart.
Main Methods:
- Application of triple-mode Floquet theory to analyze recoupling sequences with non-vanishing effective fields.
- Derivation and analysis of a homonuclear double-quantum recoupling sequence from the C72(1) symmetry-based sequence.
- Analytical calculations of second-order effective Hamiltonians to assess cross-term suppression.
- Experimental and numerical simulations to validate theoretical predictions.
Main Results:
- The developed triple-mode Floquet theory framework successfully analyzes asynchronous recoupling sequences.
- The novel asynchronous sequence demonstrates superior performance for spin pairs with small dipolar couplings and large chemical-shift anisotropy.
- The resonance condition of the new sequence is accurately described by the theoretical framework.
- The asynchronous sequence shows improved suppression of second-order cross terms compared to rotor-synchronized methods.
Conclusions:
- Triple-mode Floquet theory provides a powerful tool for understanding asynchronous recoupling sequences in NMR.
- The newly developed asynchronous recoupling sequence offers significant advantages for specific experimental scenarios.
- This work advances the design and application of advanced pulse sequences in solid-state NMR spectroscopy.
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