Half-integer spin quadrupolar nuclei

Goldbourt, A. and Madhu, P.K. (2005) Multiple-quantum magic-angle spinning high-resolution NMR spectroscopy of half-integer spin quadrupolar nuclei. Annu. Rep. NMR Spectrosc., 54, 81-153. 

Even if the optimisation of the use of DFS, RAPT or adiabatic inversion pulses is not straightforward for nuclei with low sensitivity, it is nonetheless worth applying one of these methods to improve sensitivity. As long as there is no influence on the CT resonance, these techniques are likely to produce an enhanced CT signal compared to standard spin-echo experiments. Therefore, for Mg (as well as for other insensitive half-integer spin quadrupolar nuclei such as S, K and Ca), it is always advisable to apply some population transfer technique before the excitation of the CT signal. 

QCPMG experiments, both for static and for spinning samples, have been extensively used for S/N ratio enhancement in experiments involving many half-integer spin quadrupolar nuclei, including Mg (as exemplified in the next section), S, Cl, and Sr. In many of these... 

M. E. Smith and E. R. H. van Eck, Recent advances in experimental solid state NMR methodology for half-integer spin quadrupolar nuclei. Prog. Nud. Magn. Reson. Spectrosc., 1999, 34,159-201. 

T. T. Nakashima, K. J. Harris and R. E. Wasylishen, Pulse FT NMR of non-equilibrium states of half-integer spin quadrupolar nuclei in single crystals. /. Magn. Reson., 2010, 202,162-172. 

MAS, half-integer spin quadrupolar nuclei central transition... 

Multinuclear (isocyanide)gold complexes, reactivity, 2, 287 Multi-phase organometallic catalysis, in ionic liquids, 1, 856 Multiple-quantum MAS, half-integer spin quadrupolar nuclei central transition NMR studies, 1, 466 Multistate magnetization transfer, in dynamic NMR magnetization, 1, 410 Multistep catalytic cycles... 

CS tensors for complex spectra, 1, 463 dicyclopentadienylberyllium compounds, 2, 74 tj4-diene and rf-allyl pseudo-rotations, 1, 416 half-integer quadrupolar nuclei, central transition, 1, 457 half-integer spin quadrupolar nuclei central transition,... 

High-Resolution Solid-State NMR of Half-Integer Spin Quadrupolar Nuclei... 

The double-rotation technique was introduced by Samoson et al. in 1988. This was the first real high-resolution method for half-integer spin quadrupolar nuclei. DOR is performed as a ID experiment in which the sample is spun simultaneously by an inner rotor that is inclined along an axis making an angle of 30.56° with respect to an outer rotor axis, and an outer rotor at an angle of 54.7° with respect to Bq. Unlike Eq. (35), here, the Hamiltonian contains instead of a product term of the form (O2)... 

For an ensemble of crystallographically equivalent nuclei with spin /, 21 NMR transitions take place. For most elements, the most abundant spin-active isotope is quadrupolar with half-integer spin. For these nuclei, spectro-scopists usually focus on the mj = 1/2 — mi = -1 /2 transition since it is not perturbed by the first-order quadrupolar interaction (i.e., to a first approximation, this transition behaves like that for a spin-1/2 nucleus, see below). Hence, an overview of the theory for half-integer spin quadrupolar nuclei is presented here. For a thorough description of the theory for the quadrupolar interaction, readers are referred to numerous texts and reviews on the topic. ... 

R. Siegel, T.T. Nakashima, R.E. Wasyhshen, Sensitivity enhancement of sohd-state NMR spectra of half-integer spin quadrupolar nuclei using hyperbohc secant pulses apphcations to spin-5/2 nuclei, Chem. Phys. Lett. 421 (2005) 529. 

MQ MAS techniques for high-resolution solid-state NMR of half-integer spin quadrupolar nuclei have been reviewed by Goldbourt and Madhu. The combination of MQ MAS with other solid-state NMR techniques, such as hetero- and homo-nuclear correlation experiments has also been considered. Other aspects, such as basic theory, experimental implementation, signal optimisation, data analysis and interpretation, signal enhancement schemes and applications have also been presented. 

Nakashima TT, Teymoori R, Wasylishen RE (2009) Using hyperbolic secant pulses to assist characterization of chemical shift tensors for half-integer spin quadrupolar nuclei in MAS powder samples. Magn Reson Chem 47 465 71... 

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