Multiple-quantum dynamics in solid state NMR

Journal Article · Sun Sep 01 00:00:00 EDT 1985 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.449344· OSTI ID:5492876

Baum, J; Munowitz, M; Garroway, A N; Pines, A

Recently developed solid state multiple-quantum NMR methods are applied to extended coupling networks, where direct dipole--dipole interactions can be used to create coherences of very high order (approx. 100). The progressive development of multiple-quantum coherence over time depends upon the formation of multiple-spin correlations, a phenomenon which also accompanies the normal decay to equilibrium of the free induction signal in a solid. Both the time development and the observed distributions of coherence can be approached statistically, with the spin system described by a time-dependent density operator whose elements are completely uncorrelated at sufficiently long times. With this point of view, we treat the distribution of coherence in a multiple-quantum spectrum as Gaussian, and characterize a spectrum obtained for a given preparation time by its variance. The variance of the distribution is associated roughly with the number of coupled spins effectively interacting, and its steady growth with time reflects the continual expansion of the system under the action of the dipolar interactions. The increase in effective system ''size'' is accounted for by a random walk model for the time development of the density operator. Experimental results are presented for hexamethylbenzene, adamantane, and squaric acid. The formation of coherence in systems containing physically isolated clusters is also investigated, and a simple method for estimating the number of spins involved is demonstrated.

• Research Organization: Department of Chemistry, University of California, Berkeley and Materials and Molecular Research Division, Lawrence Berkeley Laboratory, Berkeley, California 94720
• OSTI ID: 5492876
• Journal Information: J. Chem. Phys.; (United States), Vol. 83:5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ADAMANTANE
NMR SPECTRA
AROMATICS
CONDENSED AROMATICS
CORRELATIONS
SOLIDS
SPIN
ALKANES
ANGULAR MOMENTUM
CYCLOALKANES
HYDROCARBONS
ORGANIC COMPOUNDS
PARTICLE PROPERTIES
SPECTRA
400301* - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)
656000 - Condensed Matter Physics