@article {434, title = {Rotational diffusion measurements of suspended colloidal particles using two-dimensional exchange nuclear magnetic resonance}, journal = {Journal of Chemical Physics}, volume = {104}, year = {1996}, note = {J Chem PhysTn837Times Cited:13Cited References Count:24}, month = {Jan 8}, pages = {509-520}, abstract = {

We present here an experimental and theoretical study of the application of two-dimensional exchange nuclear magnetic resonance spectroscopy (NMR) to the investigation of the rotational diffusion of colloidal particles. The theoretical discussion includes the nature of the NMR frequency time-correlation function where the NMR interaction is represented by the chemical shift anisotropy (CSA). Time-correlation functions for the isotropic rotational diffusion of a suspension of colloidal particles containing single and multiple sites are derived in addition to time-correlation functions for the rotational diffusion of a suspension of symmetric top particles containing an isotropic distribution of a single CSA interaction. Simulations of two-dimensional exchange spectra for particles undergoing isotropic rotational diffusion are presented. We performed two-dimensional exchange NMR experiments on a colloidal suspension of spherical poly(methyl methacrylate) (PMMA) particles which were synthesized with a 20\% enrichment in C-13 at the carbonyl site. Rotational diffusion time-correlation functions determined from the experimental exchange spectra are consistent with the composition of the colloidal suspension. Detailed explanations of the syntheses of the enriched methyl C-13-(carbonyl)-methacrylate monomer and the small quantities of 20\% enriched C-13-(carbonyl)-poly(methyl methacrylate) microspheres used for this study are presented. (C) 1996 American Institute of Physics.

}, keywords = {scattering}, isbn = {0021-9606}, doi = {Doi 10.1063/1.470847}, url = {://WOS:A1996TN83700009}, author = {Barrall, G. A. and Schmidt-Rohr, K. and Lee, Y. K. and Landfester, K. and Zimmermann, H. and Chingas, G. C. and Pines, A.} } @article {439, title = {Spin-Polarized Xe-129 Gas Imaging of Materials}, journal = {Journal of Magnetic Resonance Series A}, volume = {115}, year = {1995}, note = {J Magn Reson Ser ARl474Times Cited:49Cited References Count:23}, month = {Jul}, pages = {127-130}, keywords = {xenon}, isbn = {1064-1858}, doi = {Doi 10.1006/Jmra.1995.1157}, url = {://WOS:A1995RL47400017}, author = {Song, Y. Q. and Gaede, H. C. and Pietrass, T. and Barrall, G. A. and Chingas, G. C. and Ayers, M. R. and Pines, A.} } @article {496, title = {Correlation of Isotropic and Anisotropic Chemical-Shifts in Solids by 2-Dimensional Variable-Angle-Spinning Nmr}, journal = {Israel Journal of Chemistry}, volume = {32}, year = {1992}, note = {Israel J ChemKt517Times Cited:29Cited References Count:19}, pages = {161-164}, abstract = {

We describe a new solid-state nuclear magnetic resonance (NMR) technique for correlating anisotropic and isotropic chemical shifts in powdered samples. Two-dimensional (2D) NMR spectra are obtained by processing signals acquired in independent experiments for different angles between the sample spinning axis and the Zeeman magnetic field. This 2D NMR approach can therefore resolve individual static anisotropic lineshapes according to their isotropic chemical shift frequencies, without use of sudden mechanical motions or multiple-pulse irradiation schemes. Applications of the technique are illustrated with an analysis of the chemical shift anisotropy for the eight distinct C-13 sites in tyrosine.

}, keywords = {magic-angle}, isbn = {0021-2148}, url = {://WOS:A1992KT51700005}, 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.} } @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 = {

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.

}, keywords = {axis}, isbn = {0021-9606}, doi = {Doi 10.1063/1.463860}, url = {://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.} }