Quadrupolar Nuclei In Solids Research Articles

Coherence transfer involving quadrupolar nuclei in solids: aluminum-27 .tautm. phosphorus-31 cross-polarization NMR in the molecular sieve VPI-5

Coherence transfer involving quadrupolar nuclei in solids: aluminum-27 .tautm. phosphorus-31 cross-polarization NMR in the molecular sieve VPI-5

NMR Characterization of Half-integer Quadrupolar Nuclei in Solids

Abstract This article describes a few aspects of NMR characterization of half-integer quadrupolar nuclei in powder samples which are either static or rotating around one fixed axis (M.A.S. and V.A.S. techniques). The simultaneous occurence of C.S.A. and quadrupole interactions with possible noncoincident tensors is discussed. Two experimental limitations are taken into accout: the sample spinning speed and the RF-amplifier power

An efficient simulation of variable-angle spinning lineshapes for the quadrupolar nuclei with half-integer spin

NMR spectroscopy of quadrupolar nuclei in solids generally yields broad lines even when magic-angle spinning is applied. Broadening of the cen t transition of quadrupolar nuclei with half-integer spins is caused by the anisotropy of the second-order quadrupolar interaction. A straightforward approach is reported which combines average-Hamiltonian theory and a numerical solution of a classical banded matrix describing the equation of motion for a quadrupolar nucleus under variable-angle sample-spinning conditions. At either of two fourth-rank magic angles, a simple three-parameter lineshape is obtained, and the three breakpoints are related directly to the quadrupolar constant and its asymmetry parameter. The banded matrix method used in the simulations is computationally much more efficient than the standard method using Bessel functions.

The influence of MAS on spin-lattice relaxation curves and nuclear spin excitation of half-integer spin quadrupolar nuclei in solids

The influence of MAS on spin-lattice relaxation curves and nuclear spin excitation of half-integer spin quadrupolar nuclei in solids

“Variable-angle” sample-spinning nuclear magnetic resonance spectroscopic studies of non-integral spin quadrupolar nuclei in solids: Analysis of spinning-sidebands for the case η=0

We present an average Hamiltonian analysis of the “variable-angle” sample-spinning nuclear magnetic resonance spectra of the central ( 1 2 , − 1 2 ) transition of the I= 3 2 nuclei 23Na (in Na 2MoO 4) and 11B (in a borosilicate glass) in the slow-spinning regime (ω r < W ( 1 2 , − 1 2 ), for a purely second-order quadrupolar interaction and an axially symmetric electric field gradient tensor. We obtain good agreement between theory and experiment. The technique is applicable to the analysis of systems with large quadrupole coupling constants, as well as to those with multiple sites and different coupling constants and chemical shifts.

Magic-angle spinning NMR spectra of satellite transitions for quadrupolar nuclei in solids

Magic-angle spinning NMR spectra of satellite transitions for quadrupolar nuclei in solids

Solid-state gallium-69 and gallium-71 nuclear magnetic resonance spectroscopic studies of gallium analog zeolites and related systems

The authors have obtained solid-state 11.7-T /sup 69/Ga and /sup 71/Ga nuclear magnetic resonance (NMR) spectra of a series of gallosilicates (gallium analogues of zeolites Na-X, Na-Y, Na-sodalite, and Na-natrolite). From the apparent /sup 69/Ga and /sup 71/Ga chemical shifts, values of the nuclear quadrupole coupling constants (e/sup 2/qQ/h) and the true, isotropic chemical shifts (delta/sub i) have been deduced for the framework, tetrahedral, Ga(OSi)/sub 4/ sites. The e/sup 2/qQ/h values are in the range 1.9-2.7 MHz for /sup 69/Ga and 1.2-1.7 MHz for /sup 71/Ga. The isotropic chemical shifts are all in the range 171-186 ppm downfield from an external standard of 1 M Ga(NO/sub 3/)/sub 3/. Their results indicate that measurement of the apparent (second-order shifted) chemical shifts for pairs of isotopes of nonintegral spin quadrupolar nuclei in solids at one magnetic field strength is a useful new approach for determination of both isotropic chemical shifts and nuclear quadrupole coupling constant values.

Solid-state spin-echo Fourier transform NMR of 39K and 67Zn salts at high field

We have used a two-pulse spin-echo sequence (with appropriate phase cycling) to obtain relatively undistorted second-order powder pattern spectra of the nonintegral spin quadrupolar nuclei 39K and 67Zn, in solids. Using the spin-echo approach, central transition breadths of up to approximately 100 kHz may be readily investigated. Results on 18-crown-6 ether · 39KNO 3 and 39K + · monensin − yield e 2 qQ/ h values of 1.80 and 3.20 MHz, with η = 0.37 and 0.52, respectively. For 67Zn(OAc) 2 · 2H 2O, e 2 qQ/ h = 5.3 MHz and η = 0.87 have been obtained. The spin-echo approach should permit investigation of a wide variety of nonintegral spin quadrupolar nuclei in solids using high-field Fourier transform methods.

Satellite transition high-resolution NMR of quadrupolar nuclei in powders

Relative shifts of the central and satellite transition lines determine the precise iosotropic chemical shifts of I = 5 2 and 9 2 quadrupolar nuclei in solids. The satellite transition is conveniently measured through the rotation sidebands.

Second-order quadrupolar echo.

A selective 180\ifmmode^\circ\else\textdegree\fi{} pulse in the z direction is shown to refocus the second-order broadening of the (1/2)-(1/2) central transition in the spin-(5/2) nucleus $^{27}\mathrm{Al}$. Evidence for this refocusing is the formation of an echo after transverse magnetization is created by a selective 90\ifmmode^\circ\else\textdegree\fi{} x pulse, and the ${p}_{z}$ pulse following the initial decay leads to a rise and decay of magnetization. Implications for high-resolution NMR of weak quadrupolar nuclei in solids are discussed.

High-resolution NMR spectroscopy of quadrupolar nuclei in solids: sodium salts

High-resolution NMR spectroscopy of quadrupolar nuclei in solids: sodium salts

Enhanced resolution in NMR of quadrupolar nuclei in solids: Interferometric correlation of the first- and second-order shifts

Enhanced resolution in NMR of quadrupolar nuclei in solids: Interferometric correlation of the first- and second-order shifts