Journal ArticleDOI
Heteronuclear decoupling in rotating solids
Andrew E. Bennett,Chad M. Rienstra,Michèle Auger,Michèle Auger,K. V. Lakshmi,K. V. Lakshmi,Robert G. Griffin +6 more
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TLDR
In this article, a simple two pulse phase modulation (TPPM) scheme was proposed to reduce the residual linewidths arising from insufficient proton decoupling power in double resonance magic angle spinning (MAS) experiments.Abstract:
A simple two pulse phase modulation (TPPM) scheme greatly reduces the residual linewidths arising from insufficient proton decoupling power in double resonance magic angle spinning (MAS) experiments. Optimization of pulse lengths and phases in the sequence produces substantial improvements in both the resolution and sensitivity of dilute spins (e.g., 13C) over a broad range of spinning speeds at high magnetic field. The theoretical complications introduced by large homo‐ and heteronuclear interactions among the spins, as well as the amplitude modulation imposed by MAS, are explored analytically and numerically. To our knowledge, this method is the first phase‐switched sequence to exhibit improvement over continuous‐wave (cw) decoupling in a strongly coupled homogeneous spin system undergoing sample spinning.read more
Citations
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Journal ArticleDOI
Spectral Editing in 13C MAS NMR under Moderately Fast Spinning Conditions
Enrico De Vita,Lucio Frydman +1 more
TL;DR: Novel procedures for the spectral assignment of peaks in high-resolution solid-state (13)C NMR are discussed and demonstrated, and Dipolar-based analogs of editing techniques that are commonly used in liquid-state NMR such as APT and INEPT can be derived, while avoiding the need for periods of homonuclear (1)H--(1) H multipulse decoupling.
Journal ArticleDOI
Low-power broadband homonuclear dipolar recoupling without decoupling: Double-quantum 13C NMR correlations at very fast magic-angle spinning
TL;DR: In this paper, a symmetry-based radio-frequency (RF) pulse sequence for efficient excitation of double-quantum (2Q) coherences under very fast (>60 kHz) magic-angle spinning (MAS) conditions was proposed.
Journal ArticleDOI
Differences in crystalline cellulose modification due to degradation by brown and white rot fungi
Anne Christine Steenkjær Hastrup,Caitlin Howell,Flemming H. Larsen,Noppadon Sathitsuksanoh,Barry Goodell,Jody Jellison +5 more
TL;DR: Differences in degradation methods previously reported among fungal species, specifically more non-enzymatic degradation in brown rot versus more enzyme-based degradation in white rot were consistent with differences observed for brown and white rot fungi.
Journal ArticleDOI
Fine structure of nacre revealed by solid state 13C and 1H NMR
Christian Jäger,Helmut Cölfen +1 more
TL;DR: In this article, solid-state NMR investigations of nacre reveal the presence of an amorphous surface layer around the aragonite platelets, which contains hydrogen carbonate groups, presumably at its outer surface and water molecules slightly hindered in their mobility in a proton ratio of 1':'33, i.e. about 16 water molecules per HCO3−unit.
Journal ArticleDOI
Refocused continuous-wave decoupling: a new approach to heteronuclear dipolar decoupling in solid-state NMR spectroscopy.
Joachim M. Vinther,Anders B. Nielsen,Morten Bjerring,Ernst R. H. van Eck,Arno P. M. Kentgens,Navin Khaneja,Niels Chr. Nielsen +6 more
TL;DR: A novel strategy for heteronuclear dipolar decoupling in magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy is presented, which eliminates residual static high-order terms in the effective Hamiltonian originating from interactions between oscillating dipolar and anisotropic shielding tensors.
References
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Journal ArticleDOI
Proton‐enhanced NMR of dilute spins in solids
TL;DR: In this article, the NMR signals of isotopically or chemically dilute nuclear spins S in solids can be enhanced by repeatedly transferring polarization from a more abundant species I of high abundance (usually protons) to which they are coupled.
Book
Principles of high-resolution NMR in solids
Abstract: 1 Introduction.- 2 Nuclear Spin Interactions in Solids.- 2.1 Basic Nuclear Spin Interactions in Solids.- 2.2 Spin Interactions in High Magnetic Fields.- 2.3 Transformation Properties of Spin Interactions in Real Space.- 2.4 Powder Spectrum Line Shape.- 2.5 The NMR Spectrum. Lineshapes and Moments.- 2.6 Magic Angle Spinning (MAS).- 2.7 Rapid Anisotropic Molecular Rotation.- 2.8 Line Shapes in the Presence of Molecular Reorientation.- 3 Multiple-Pulse NMR Experiments.- 3.1 Idealized Multiple-Pulse Sequences.- 3.2 The Four-Pulse Sequence (WHH-4).- 3.3 Coherent Averaging Theory.- 3.4 Application of Coherent Averaging Theory to Multiple-Pulse Sequences.- 3.5 Arbitrary Rotations and Finite Pulse Width in Multiple-Pulse Experiments.- 3.6 Second Averaging.- 3.7 The Influence of Pulse Imperfections on Multiple-Pulse Experiments.- 3.8 Resolution of Multiple-Pulse Experiments.- 3.9 Magic Angle Rotating Frame Line Narrowing Experiments.- 3.10 Modulation Induced Line Narrowing.- 3.11 Applications of Multiple-Pulse Experiments.- 4 Double Resonance Experiments.- 4.1 Basic Principles of Double Resonance Experiments.- 4.2 Cross-Polarization of Dilute Spins.- 4.3 Cross-Polarization Dynamics.- 4.4 Spin-Decoupling Dynamics.- 4.5 Application of Cross-Polarization Experiments.- 5 Two-Dimensional NMR Spectroscopy.- 5.1 Basic Principles of 2 D-Spectroscopy.- 5.2 2D-Spectroscopy of 13C-1H Interactions in Solids.- 5.3 Applications of 2D-Spectroscopy.- 6 Multiple-Quantum NMR Spectroscopy.- 6.1 Double-Quantum Decoupling.- 6.2 The Three-Level System Double Quantum Coherence.- 6.3 Multiple-Quantum Coherence.- 6.4 Selective Multiple-Quantum Coherence.- 6.5 Double-Quantum Cross-Polarization.- 7 Magnetic Shielding Tensor.- 7.1 Ramsey's Formula.- 7.2 Approximate Calculations of the Shielding Tensor.- 7.3 Proton Shielding Tensors.- 7.4 19F Shielding Tensors.- 7.5 13C Shielding Tensors.- 7.6 Other Shielding Tensors.- 8 Spin-Lattice Relaxation.- 8.1 Spin-Lattice Relaxation in the Weak Collision Limit.- 8.2 Spin-Lattice Relaxation in Multiple-Pulse Experiments.- 8.3 Application of Multiple-Pulse Experiments to the Investigation of Spin-Lattice Relaxation.- 8.4 Spin-Lattice Relaxation in Dilute Spin Systems.- 8.5 Selective Excitation and Spectral Diffusion.- 9 Appendix.- A Irreducible Tensor Representation of Spin Interactions.- B Rotations.- C General Line Shape Theory.- D Homogeneous, Inhomogeneous and Heterogeneous Lineshapes.- E Lineshape and Relaxation due to Fluctuating Chemical Shift Tensors.- F Time Evolution and Magnus Expansion.- G Coherent Versus Secular Averaging Theory.- H Applications of Average Hamiltonian Theory.- I Relaxation Theory.- 10 References.- 11 Subject Index.
Journal ArticleDOI
Nuclear Magnetic Resonance Spectra from a Crystal rotated at High Speed
TL;DR: In this article, it was shown that when these weak side-spectra are included the second moment does indeed remain invariant even though the second moments of the central portion, which is all that is observed experimentally, becomes smaller.
Journal ArticleDOI
Carbon-13 nuclear magnetic resonance of polymers spinning at the magic angle
Journal ArticleDOI
An improved sequence for broadband decoupling: WALTZ-16
TL;DR: In this paper, the effects of the proton irradiation sequence by means of a train of spin rotation operators, the overall effect at the end of the cycle being calculated by explicit matrix multiplication, the offset dependence of this proton response determined the residual splitting of the carbon-13 resonance and hence the effectiveness of the decoupling.