Relaxation (NMR)

About: Relaxation (NMR) is a research topic. Over the lifetime, 29342 publications have been published within this topic receiving 689851 citations.

[ReCl4(CN)2]2-: a high magnetic anisotropy building unit giving rise to the single-chain magnets (DMF)4MReCl4(CN)2 (M = Mn, Fe, Co, Ni).

Abstract: An S = 3/2, high-anisotropy building unit, trans-[ReCl4(CN)2]2−, representing the first paramagnetic complex with a mixture of just cyanide and halide ligands, has been synthesized through the reaction of (Bu4N)CN with ReCl4(THF)2. This species is characterized in detail and employed in directing the formation of a series of one-dimensional coordination solids of formula (DMF)4MReCl4(CN)2 (M = Mn (2), Fe (3), Co (4), Ni (5)). Variable-temperature dc magnetic susceptibility measurements demonstrate the presence of intrachain antiferromagnetic (2) and ferromagnetic (3−5) exchange coupling within these solids. In addition, probing the ac magnetic susceptibility as a function of both temperature and frequency reveals that all of the chain compounds exhibit slow relaxation of the magnetization. The relaxation time is shown to be thermally activated, with energy barriers to relaxation of Δτ = 31, 56, 17, and 20 cm−1 for 2−5, respectively. Notably, the field-dependent magnetization of the iron congener exhibits ...

Transverse relaxivity of particulate MRI contrast media: from theories to experiments.

Abstract: Computer simulations and experimental approach have been used to characterize the properties of particulate MRI contrast agents with special attention paid to the influence of particle size. Up to approximately 50 nm, an increase of the particle diameter leads to a strong enhancement of the transverse magnetization decay rate. For larger grains or aggregates, the decay rate measured without spin-echo formation reaches a plateau. When observed through a spin-echo sequence, the transverse magnetization decay rate becomes slower on increasing the particle size or on shortening the echo time. For these large particles, multiexponential decay rates are observed. Definition and measurement of relaxivity in such systems is discussed. © 1991 Academic Press, Inc.

Molecular diffusion and nuclear-magnetic-resonance relaxation of water in unsaturated porous silica glass

Abstract: Measurements have been performed of the nuclear-magnetic-resonance longitudinal and transverse relaxation and the self-diffusion coefficient of deionized water confined in the porous space of a silica glass. The average pore diameter of the glass is 3.5 nm, and the experiments were conducted with different degrees of fluid filling. All three physical quantities were found to be linearly dependent on filling provided this was in excess of the amount of water corresponding to one monolayer, in agreement with theoretical predictions based on geometrical considerations. However, a deviation is observed below one monolayer, which is interpreted as a modification of the liquid-solid interface interaction, which causes the water molecules to become less mobile.