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A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference
Published on: September 5, 2019
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Sensitivity enhancement by multiple-contact cross-polarization under magic-angle spinning.
1Institut de Chimie, UMR 7177 CNRS, Université de Strasbourg, Strasbourg, France.
Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|June 30, 2017
Summary
Multiple-contact cross-polarization (MC-CP) enhances polarization in solid-state NMR. This method offers higher efficiency than optimized techniques, especially when magic-angle spinning frequencies match heteronuclear couplings.
Area of Science:
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
- Advanced pulse sequence development for enhanced sensitivity.
Background:
- Cross-polarization (CP) is crucial for sensitivity enhancement in solid-state NMR.
- Magic-angle spinning (MAS) is vital for high-resolution spectra of powder samples.
- Existing methods like Hartmann-Hahn CP (HHCP) and adiabatic passage HHCP (APHH-CP) have limitations.
Purpose of the Study:
- To analytically describe and evaluate the Multiple-Contact Cross-Polarization (MC-CP) technique.
- To compare MC-CP performance against established CP methods under MAS conditions.
- To determine optimal conditions and limitations for MC-CP experiments.
Main Methods:
- Application of MC-CP to ferrocene and l-alanine powder samples.
- Analytical description using density matrix formalism.
- Combination of two-step memory function and Anderson-Weiss approximation for approximate solutions.
Main Results:
- MC-CP achieves higher polarization at short contact times than optimized APHH-CP when MAS frequency is near heteronuclear dipolar coupling.
- MC-CP exhibits broader Hartmann-Hahn (HH) sideband conditions compared to single-contact HHCP.
- Rotor-asynchronous equilibrations can restore efficient centerband HH condition polarization transfer.
Conclusions:
- MC-CP is a robust technique, particularly advantageous when standard APHH-CP is challenging.
- The broader sideband conditions of MC-CP offer flexibility in experimental setup.
- Understanding repolarization boundary conditions is key for successful MC-CP implementation.
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