Spin-1/2 nuclides

The classical Jeener Broekaert sequence (133) is used to determine the dipolar-order relaxation time (in systems of spin 1/2 nuclides) and the Tiq relaxation time (in systems with spin 1 nuclides) of spin 1 nuclides with quadrupolar contributions to 7. Its FFC version is similar to the Inversion Recovery, except that the first 180° pulse is replaced by the sequence 90, — 5 — 45, the detection pulse becomes 45 and a special phase cycle is required. We shall not dwell on the details and purpose of the sequence since they go beyond the scope of this chapter. We wish to underline, however, the fact that sequences of this type require a close coordination of the preparatory sub-sequence with the signal-detection sub-sequence in order to isolate not just a particular magnetization component but a particular relaxation pathway. 

Magnetic Resonance of Systems with Equivalent Spin-1/2 Nuclides... 

The situation has been elucidated in a series of recent papers Magnetic resonance in systems with equivalent spin-1/2 nuclides. 13 1 38 39 These works deal with EPR examples, that is each with an impaired electron exposed to a set of n equivalent 1=1/2 nuclei. For our present purpose, we can deem the electron to have been replaced by some spin-bearing nucleus to be examined by NMR. 

S. M. Nokhrin, J. A. Weil and D. F. Howarth, Magnetic resonance in systems with equivalent spin-1/2 nuclides. Part 1. J. Magn. Reson., 2005,174, 209-218. 

It is my pleasure to present Volume 71 of Annual Reports on NMR, which consists of a collection of reports on advances in many scientific areas due to the application of NMR techniques. The volume commences with an account of Magnetic Resonance of Systems with Equivalent Spin-1/2 Nuclides by J.A. Weil Protein Dynamics as Reported by NMR is presented by Z. Gaspari and A. Perczel Virtual MRS Spectral Simulation and its Applications is covered by B.J. Soher, K. Young and L. Kaiser F.H. Larsen reports on Simulation of Molecular Motion of Quadrupolar Nuclei in Solid State NMR finally, NMR Studies of Disorder in Condensed Matter Systems is discussed by K.P. Ramesh. My thanks are due to all of these reporters for their interesting and timely contributions. 

To understand the varied chemistry of the aluminas, techniques need to be developed for studying the surface independent of the bulk. Structural and dynamical aspects of the surface do have their origins in the bulk, but the specific details delineating the surface will be different. Clearly it would be advantageous to apply the same surface selective CP methodology developed for the silicas [12-16] to the surface of the aluminas. Before addressing this particular point, however, we need to consider the feasibility of the experiment. Are the aluminum atoms at the surface indeed observable by NMR methods If surface aluminum atoms are observable, we must then recognize that the spin of interest, Al, is not a spin-1/2 nuclide (/ for Al is 5/2) hence Al has a nonzero nuclear electric quadrupole moment. Cross-polarization from protons to a quadrupolar nucleus presents the experimenter with another layer of complication in compari-... 

A.W. MacGregor, L.A. O Dell, R.W. Schurko, New methods for the acquisition of ultra-widehne soHd-state NMR spectra of spin-1/2 nuclides, J. Magn. Reson. 208 (2011) 103-113. 

The spin properties of the magnetic nuclides of silicon, germanium, tin, and lead are described. Each has a useful spin 1/2 nuclide, except for germanium. Experimental methods are discussed, including those of importance because of the long relaxation times frequently encountered (especially for Si). Data on relaxation times, chemical shifts, and coupling constants are briefly reviewed. 

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