@article {480,
	title = {Variable-Angle 3-Dimensional Exchange Nuclear-Magnetic-Resonance Spectroscopy for the Study of Molecular-Motion in Complex Solids},
	journal = {Journal of the American Chemical Society},
	volume = {115},
	year = {1993},
	note = {J Am Chem SocLf062Times Cited:14Cited References Count:23},
	month = {Jun 2},
	pages = {4825-4829},
	abstract = {<p>Although molecular motions are responsible for many of the macroscopic properties observed in solids, especially in polymers, methods for studying these processes in all but the simplest systems are scarce. In the present study we introduce a three-dimensional nuclear magnetic resonance experiment for characterizing ultraslow molecular motions in complex solid systems. The technique extracts dynamic information by resolving the two-dimensional exchange distributions that can be observed in spectra of static samples, according to the isotropic chemical shifts of individual molecular sites. These three-dimensional correlations are achieved by processing signals arising from a fast-spinning solid sample using two independent macroscopic axes of rotation as extraction parameters, an approach which becomes practical due to the simple scaling behavior of anisotropic chemical shifts with respect to the axis of sample rotation. The principles involved in this new spectroscopic technique are discussed, and the method is illustrated with an application to the analysis of motions in isotactic polypropylene.</p>
},
	keywords = {jumps},
	isbn = {0002-7863},
	doi = {Doi 10.1021/Ja00064a050},
	url = {<Go to ISI>://WOS:A1993LF06200050},
	author = {Frydman, L. and Lee, Y. K. and Emsley, L. and Chingas, G. C. and Pines, A.}
}
@article {497,
	title = {Variable-Angle Correlation Spectroscopy in Solid-State Nuclear-Magnetic-Resonance},
	journal = {Journal of Chemical Physics},
	volume = {97},
	year = {1992},
	note = {J Chem PhysJr338Times Cited:90Cited References Count:28},
	month = {Oct 1},
	pages = {4800-4808},
	abstract = {<p>We describe here a new solid-state nuclear-magnetic-resonance (NMR) experiment for correlating anisotropic and isotropic chemical shifts of inequivalent nuclei in powdered samples. Spectra are obtained by processing signals arising from a spinning sample, acquired in independent experiments as a function of the angle between the axis of macroscopic rotation and the external magnetic field. This is in contrast to previously proposed techniques, which were based on sudden mechanical flippings or multiple-pulse sequences. We show that the time evolution of variable-angle-spinning signals is determined by a distribution relating the isotropic frequencies of the spins with their corresponding chemical shift anisotropies. Fourier transformation of these data therefore affords a two-dimensional NMR spectrum, in which line shapes of isotropic and anisotropic interactions are correlated. Theoretical and experimental considerations involved in the extraction of this spectral information are discussed, and the technique is illustrated by an analysis of C-13 NMR anisotropy in glycine, cysteine, and p-anisic acid.</p>
},
	keywords = {axis},
	isbn = {0021-9606},
	doi = {Doi 10.1063/1.463860},
	url = {<Go to ISI>://WOS:A1992JR33800022},
	author = {Frydman, L. and Chingas, G. C. and Lee, Y. K. and Grandinetti, P. J. and Eastman, M. A. and Barrall, G. A. and Pines, A.}
}
