The theory of nuclear magnetic resonance (NMR) on a solid sample containing pairs of coupled homonuclear spins-1/2, rotating in a large magnetic field, is presented. The time dependence introduced by the sample rotation, in conjunction with the spin–spin coupling, makes it appear that each of the central two levels in the four-level system split into a pair of ‘‘virtual states.’’ Each of the eight possible single-quantum coherences between the virtual states and the two outer levels in general contribute to the spectrum, although four of these contributions are forbidden unless a rotational resonance occurs (matching of an integer multiple of the spinning speed with the difference in isotropic shifts). Analytical line shapes for the case of vanishing shift anisotropy are given and techniques for numerical simulation in the general case demonstrated. The theory of Zeeman magnetization exchange in the presence of zero-quantum dephasing is presented.

In this paper we collect and detail recent results concerning 77Se and 13C nuclear relaxation rate measurements obtained on several representatives of the (TMTSF)2X and (TMTTF)2X series of charge transfer salts as a function of temperature and hydrostatic pressure. From the temperature and pressure dependences of T-11, for the compounds (TMTTF)2PF6, (TMTTF)2Br, (TMTSF)2PF6 and (TMTSF)2ClO4, we are in a position to extract the nature, the amplitude, the statics, the dynamics and finally the dimensionality of spin correlations that characterize the unified phase diagram of both series of materials

Rotationally resonant magnetization exchange, a new nuclear magnetic resonance (NMR) technique for measuring internuclear distances between like spins in solids, was used to determine the distance between the C-8 and C-18 carbons of retinal in two model compounds and in the membrane protein bacteriorhodopsin. Magnetization transfer between inequivalent spins with an isotropic shift separation, delta, is driven by magic angle spinning at a speed omega r that matches the rotational resonance condition delta = n omega r, where n is a small integer. The distances measured in this way for both the 6-s-cis- and 6-s-trans-retinoic acid model compounds agreed well with crystallographically known distances. In bacteriorhodopsin the exchange trajectory between C-8 and C-18 was in good agreement with the internuclear distance for a 6-s-trans configuration [4.2 angstroms (A)] and inconsistent with that for a 6-s-cis configuration (3.1 A). The results illustrate that rotational resonance can be used for structural studies in membrane proteins and in other situations where diffraction and solution NMR techniques yield limited information.

The fatigue fracture surfaces of a metallic alloy, and the stress corrosion fracture surfaces of glass are investigated as a function of crack velocity. It is shown that in both cases, there are two fracture regimes, which have a well defined self-affine signature. At high enough length scales, the universal roughness index ζ ≃ 0.78 is recovered. At smaller length scales, the roughness exponent is close to ζc ≃ 0.50. The crossover length ξc separating these two regimes strongly depends on the material, and exhibits a power-law decrease with the measured crack velocity ξc ∝ v −φ , with φ ≃ 1. The exponents ν and β characterising the dependence of ξc and v upon the pulling force are shown to be close to ν ≃ 2 and β ≃ 2.