Articles | Volume 2, issue 1
https://doi.org/10.5194/mr-2-523-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/mr-2-523-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Effects of radial radio-frequency field inhomogeneity on MAS solid-state NMR experiments
Kathrin Aebischer
Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
Zdeněk Tošner
Department of Chemistry, Faculty of Science, Charles University, Hlavova 8, 12842 Prague 2, Czech Republic
Physical Chemistry, ETH Zürich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland
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Kathrin Aebischer, Lea Marie Becker, Paul Schanda, and Matthias Ernst
Magn. Reson., 5, 69–86, https://doi.org/10.5194/mr-5-69-2024, https://doi.org/10.5194/mr-5-69-2024, 2024
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To characterize the amplitude of dynamic processes in molecules, anisotropic parameters can be measured using solid-state NMR. However, the timescales of motion that lead to such a scaling of the anisotropic interactions are not clear. Using numerical simulations in small spin systems, we could show that mostly the magnitude of the anisotropic interaction determines the range of timescales detected by the scaled anisotropic interaction, and experimental parameters play a very minor role.
Kathrin Aebischer, Nino Wili, Zdeněk Tošner, and Matthias Ernst
Magn. Reson., 1, 187–195, https://doi.org/10.5194/mr-1-187-2020, https://doi.org/10.5194/mr-1-187-2020, 2020
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Resonant pulses in a spin-lock frame are used to select parts of the rf-field distribution in NMR experiments. Such pulses can be implemented in a straightforward way and arbitrarily shaped pulses can be used. We show an application of such pulses in homonuclear decoupling where restricting the amplitude distribution of the rf field leads to improved performance.
Luzian Thomas and Matthias Ernst
Magn. Reson. Discuss., https://doi.org/10.5194/mr-2024-13, https://doi.org/10.5194/mr-2024-13, 2024
Revised manuscript accepted for MR
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The paper investigates the suitability of an existing solution-state NMR spin decoupling sequence for use as a low-power solid-state NMR decoupling sequence under sample spinning. Complications arise from resonance conditions between the spin modulations by the pulse sequence and the sample rotation. We show that the timing of the pulse sequence is the most important criterion to achieve good decoupling. The paper gives recommendations for optimum parameters.
Kathrin Aebischer, Lea Marie Becker, Paul Schanda, and Matthias Ernst
Magn. Reson., 5, 69–86, https://doi.org/10.5194/mr-5-69-2024, https://doi.org/10.5194/mr-5-69-2024, 2024
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To characterize the amplitude of dynamic processes in molecules, anisotropic parameters can be measured using solid-state NMR. However, the timescales of motion that lead to such a scaling of the anisotropic interactions are not clear. Using numerical simulations in small spin systems, we could show that mostly the magnitude of the anisotropic interaction determines the range of timescales detected by the scaled anisotropic interaction, and experimental parameters play a very minor role.
Andrej Šmelko, Jan Blahut, Bernd Reif, and Zdeněk Tošner
Magn. Reson., 4, 199–215, https://doi.org/10.5194/mr-4-199-2023, https://doi.org/10.5194/mr-4-199-2023, 2023
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We present a tutorial on the cross-polarization experiment, which has been the main method of magnetization transfer in solid-state NMR for decades. We explain the principles of its volume-selective performance in the presence of magic angle spinning and radiofrequency field inhomogeneity and the decrease in efficiency with increasing sample rotation frequency.
Aaron Himmler, Mohammed M. Albannay, Gevin von Witte, Sebastian Kozerke, and Matthias Ernst
Magn. Reson., 3, 203–209, https://doi.org/10.5194/mr-3-203-2022, https://doi.org/10.5194/mr-3-203-2022, 2022
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Dynamic nuclear polarization requires a waveguide that connects the cold (1–10 K) sample space to the outside. To reduce the heating of the sample, a waveguide is produced from steel which has low thermal conductivity but attenuates the microwaves. Therefore, the inside of the waveguide should be plated with silver to reduce electrical losses. We show a new simple way to electroplate such waveguides with a thin silver layer and show that this improves the experimental performance.
Václav Římal, Morgane Callon, Alexander A. Malär, Riccardo Cadalbert, Anahit Torosyan, Thomas Wiegand, Matthias Ernst, Anja Böckmann, and Beat H. Meier
Magn. Reson., 3, 15–26, https://doi.org/10.5194/mr-3-15-2022, https://doi.org/10.5194/mr-3-15-2022, 2022
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Through the advent of fast magic-angle spinning and high magnetic fields, the spectral resolution of solid-state NMR spectra has recently been greatly improved. To take full advantage of this gain, the magnetic field must be stable over the experiment time of hours or even days. We thus monitor the field by simultaneous acquisition of a frequency reference (SAFR) and use this information to correct multidimensional spectra improving resolution and availability of productive magnet time.
Matías Chávez, Thomas Wiegand, Alexander A. Malär, Beat H. Meier, and Matthias Ernst
Magn. Reson., 2, 499–509, https://doi.org/10.5194/mr-2-499-2021, https://doi.org/10.5194/mr-2-499-2021, 2021
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Sample rotation around the magic angle averages out the dipolar couplings in homonuclear spin systems in a first-order approximation. However, in higher orders, residual coupling terms remain and lead to a broadening of the spectral lines. We investigate the source of this broadening and the effects on the powder line shape in small spin systems with and without chemical shifts. We show that one can expect different scaling behavior as a function of the spinning frequency for the two cases.
Kathrin Aebischer, Nino Wili, Zdeněk Tošner, and Matthias Ernst
Magn. Reson., 1, 187–195, https://doi.org/10.5194/mr-1-187-2020, https://doi.org/10.5194/mr-1-187-2020, 2020
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Resonant pulses in a spin-lock frame are used to select parts of the rf-field distribution in NMR experiments. Such pulses can be implemented in a straightforward way and arbitrarily shaped pulses can be used. We show an application of such pulses in homonuclear decoupling where restricting the amplitude distribution of the rf field leads to improved performance.
Johannes Hellwagner, Liam Grunwald, Manuel Ochsner, Daniel Zindel, Beat H. Meier, and Matthias Ernst
Magn. Reson., 1, 13–25, https://doi.org/10.5194/mr-1-13-2020, https://doi.org/10.5194/mr-1-13-2020, 2020
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This paper analyzes a commonly used line-narrowing mechanism (homonuclear decoupling) in solid-state NMR and discusses what limits the achievable line width. Based on theoretical considerations, the contribution of different effects to the line width is discussed and a new contributing term is identified. This research allows us to evaluate new ways to improve the line width in such homonuclear decoupled spectra.
Related subject area
Field: Solid-state NMR | Topic: Theory
Performance of the cross-polarization experiment in conditions of radiofrequency field inhomogeneity and slow to ultrafast magic angle spinning (MAS)
Residual dipolar line width in magic-angle spinning proton solid-state NMR
Heteronuclear and homonuclear radio-frequency-driven recoupling
Origin of the residual line width under frequency-switched Lee–Goldburg decoupling in MAS solid-state NMR
Andrej Šmelko, Jan Blahut, Bernd Reif, and Zdeněk Tošner
Magn. Reson., 4, 199–215, https://doi.org/10.5194/mr-4-199-2023, https://doi.org/10.5194/mr-4-199-2023, 2023
Short summary
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We present a tutorial on the cross-polarization experiment, which has been the main method of magnetization transfer in solid-state NMR for decades. We explain the principles of its volume-selective performance in the presence of magic angle spinning and radiofrequency field inhomogeneity and the decrease in efficiency with increasing sample rotation frequency.
Matías Chávez, Thomas Wiegand, Alexander A. Malär, Beat H. Meier, and Matthias Ernst
Magn. Reson., 2, 499–509, https://doi.org/10.5194/mr-2-499-2021, https://doi.org/10.5194/mr-2-499-2021, 2021
Short summary
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Sample rotation around the magic angle averages out the dipolar couplings in homonuclear spin systems in a first-order approximation. However, in higher orders, residual coupling terms remain and lead to a broadening of the spectral lines. We investigate the source of this broadening and the effects on the powder line shape in small spin systems with and without chemical shifts. We show that one can expect different scaling behavior as a function of the spinning frequency for the two cases.
Evgeny Nimerovsky, Kai Xue, Kumar Tekwani Movellan, and Loren B. Andreas
Magn. Reson., 2, 343–353, https://doi.org/10.5194/mr-2-343-2021, https://doi.org/10.5194/mr-2-343-2021, 2021
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The RFDR sequence has been widely used for homonuclear recoupling. The paper describes a heteronuclear version of RFDR. HET-RFDR sequence transfers longitudinal polarization between heteronuclear pairs by applying RFDR on two channels simultaneously. We perform an operator analysis of HET-RFDR and RFDR. Such an analysis allows for better understanding of the influence of offsets and paths of magnetization transfers for both these experiments, as well as the crucial role of XY phase cycling.
Johannes Hellwagner, Liam Grunwald, Manuel Ochsner, Daniel Zindel, Beat H. Meier, and Matthias Ernst
Magn. Reson., 1, 13–25, https://doi.org/10.5194/mr-1-13-2020, https://doi.org/10.5194/mr-1-13-2020, 2020
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This paper analyzes a commonly used line-narrowing mechanism (homonuclear decoupling) in solid-state NMR and discusses what limits the achievable line width. Based on theoretical considerations, the contribution of different effects to the line width is discussed and a new contributing term is identified. This research allows us to evaluate new ways to improve the line width in such homonuclear decoupled spectra.
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Short summary
The radio-frequency (rf) field amplitude in solid-state NMR probes changes over the sample volume, i.e. different parts of the sample will experience different nutation frequencies. If the sample is rotated inside the coil as it is typical for magic angle spinning in solid-state NMR, such a position-dependent inhomogeneity leads to an additional time dependence of the rf field amplitude. We show that such time-dependent modulations do not play an important role in many experiments.
The radio-frequency (rf) field amplitude in solid-state NMR probes changes over the sample...