Theory of heteronuclear decoupling in solid-state nuclear magnetic resonance using multipole-multimode Floquet theory (original) (raw)
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A simple model for heteronuclear spin decoupling in solid-state NMR
Chemical Physics Letters, 2000
We propose a simple model to describe heteronuclear spin decoupling in solid-state NMR under magic-angle sample Ž. Ž. spinning MAS. It is based on a coherent description of two heteronuclear dipolar-coupled spins I and S and an incoherent description of the interaction of the I-spin with a large number of other I-spins. The abundant and strongly coupled I-spins are irradiated. The selected I-spin is coupled by a spin-diffusion type superoperator to the I-spin bath, and this coupling is described by a single spin-diffusion rate constant. Such a model allows us to simulate efficiently the behavior of a spin system under heteronuclear decoupling in the case of CW irradiation as well as in the case of phase-modulated sequences such as TPPM.
Chemical Physics Letters, 2008
Internuclear couplings between selected homonuclear spin pairs in a multiplylabelled spin system are determined by NMR spin echo experiments in the solid state. The spin echoes are induced by an amplitude-modulated shaped pulse. The time shift in the echo modulation curve is treated by average Hamiltonian theory and verified by numerical simulation. The J-couplings may be estimated by experiments on samples spinning at the magic angle, while the direct dipoledipole couplings may be estimated by off-magic-angle spinning. The concept is tested on a uniformly 13 C-enriched sample of L-histidine hydrochloride monohydrate.
Molecular Dynamics and Magic Angle Spinning NMR
Journal of the American Chemical Society, 1994
The observation of "disappearing lines" or the inability to observe expected resonances in magic angle spinning (MAS) NMR spectra suggest an interference phenomenon between molecular dynamics and the characteristic frequencies of pulse trains and radiofrequency (RF) fields employed in the NMR experiments. In this paper, we present a systematic study of 3-fold hopping of the-NH3+ group in L-alanine, and the motion's interference with two widely-used techniques for homo-and heteronuclear decoupling. It is demonstrated experimentally and theoretically that rates of 3-fold hopping in the vicinity of the cycle times of homonuclear pulse trains or the reciprocal of the heteronuclear decoupling field strengths lead to dramatic broadening of NMR lines in MAS spectra.
Advances in Theory of Solid-State Nuclear Magnetic Resonance
Journal of nature and science
Recent advances in theory of solid state nuclear magnetic resonance (NMR) such as Floquet-Magnus expansion and Fer expansion, address alternative methods for solving a time-dependent linear differential equation which is a central problem in quantum physics in general and solid-state NMR in particular. The power and the salient features of these theoretical approaches that are helpful to describe the time evolution of the spin system at all times are presented. This review article presents a broad view of manipulations of spin systems in solid-state NMR, based on milestones theories including the average Hamiltonian theory and the Floquet theory, and the approaches currently developing such as the Floquet-Magnus expansion and the Fer expansion. All these approaches provide procedures to control and describe the spin dynamics in solid-state NMR. Applications of these theoretical methods to stroboscopic and synchronized manipulations, non-synchronized experiments, multiple incommensur...
Journal of Magnetic Resonance, 1997
The multidimensional experiment which includes isocorrelating anisotropic interactions of different spins in solids rotropic-shift evolutions for resolving signals requires the evotating at the magic angle. Anisotropic interactions, such as heterolution periods, each of which is dominated by a single type of nuclear dipolar couplings and chemical-shift anisotropies, are reanisotropic interaction under MAS (magic-angle spinning) covered in the evolution periods by newly designed RF pulse seconditions. In this study, we have developed RF multipulses quences. Calculated spectra for this correlation experiment for recovering chemical-shift anisotropy and CH dipolar independed on the mutual orientation of tensorial interactions. Thus, teraction under MAS. These pulse sequences were applied this method can provide structural information, e.g., dihedral to uniformly 13 C-labeled L-alanine. Experimental results for angles, for spin pairs distinguished by isotropic chemical shift. the correlation experiments with the multipulses are com-Experimental and numerically simulated results are presented for pared with numerical calculations to analyze the dependence L-alanine fully labeled with 13 C nuclei.
Truncated dipolar recoupling in solid-state nuclear magnetic resonance
Chemical Physics Letters, 2006
We describe a solid-state NMR concept for the estimation of individual spinspin couplings in strongly-coupled homonuclear spin systems. A radiofrequency pulse sequence, synchronized with the magic-angle sample rotation, recouples zero-quantum dipolar interactions as well as a frequency-dispersing interaction such as the chemical shift anisotropy. The combination of these two recoupled interactions causes the spin system to behave in an approximately weaklycoupled fashion. Individual spin-spin couplings may then be disentangled by using frequency-selective radiofrequency pulses. Theoretical results and numerical simulations are compared with experimental data for the 13 C nuclei in