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1H NMR spin-lattice (T1) and spin-spin (T2) relaxation times have been measured for the residual CHCl3 component of deuterochloroform (99.8 atom% D) in neat solvent samples and in a series of isotropic solutions of the ionic surfactant n-octylammonium-n-octadecanoate and also in degassed/dried and aerated solvent systems at 298 K. Analysis of the proton relaxation times as composite values from various relaxation mechanisms suggests that the spin-lattice process is predominantly via spin-rotation while spin-spin relaxation principally involves 1H-Cl scalar coupling. Rotational correlation times from relaxation rates via the dipolar and spin-rotation mechanisms reveal similar fast picosecond molecular rotation of chloroform in the different samples. The presence of surfactant in the solution appreciably affects the 1H NMR spin-lattice relaxation time of CHCl3 and the chemical shift, which is concentration dependent owing to weak intermolecular interactions. Effects of sample condition and solvent degassing, drying, and aeration treatments on the NMR relaxation times and line shape properties of the residual CHCl3 isotopomers are also examined. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the effect of the type of substituent of the cellulose ethers and the molecular mass on the state and dynamics of water in the respective hydrogels to specify the quantity of adsorbed water on the polymers or, more explicitly, to calculate the average number of water molecules bound to a polymer repeating unit (PRU).1H NMR relaxation experiments were performed on equilibrated systems of cellulose ether polymers (HEC, HPC, HPMC K4M, and HPMC K100M) with water. In particular, the water proton spinlattice ( T 1) and spin-spin ( T 2) relaxation times were measured in these systems at room temperature. The observed proton NMR T 1 and T 2 of water in hydrogels at different cellulose ether concentrations at room temperature were shown to decrease with increasing polymer concentration. The relaxation rate 1/ T 1 is sensitive to the type of polymer substituent but insensitive to the polymer molecular mass. The rate 1/ T 2 appears much less influenced by the polymer substitution. The procedure developed for calculating the amount of water bound per PRU, based on the analysis of the T 1 and T 2 data, shows that this amount is the largest for HPC followed by HEC, HP MC K4M, and HPMC K100M. The results correlate well with the degree of hydrophilic substitution of the polymer chains. This NMR analysis deals with a single molecular layer of adsorbed water for the investigated cellulose ether polymers at all concentrations, while the rest of the water in the hydrogel is bulk-like. Therefore, the mesh size of polymer network in the view of a single molecular layer is not effectively changed. [ABSTRACT FROM AUTHOR]

Muon spin rotation (μSR) and relaxation has been used to study the local magnetic structure of K3Fe5F15. A collinear F--μ+--F "hydrogen bond-like" symmetric double minimum type complex with a F…F distance of 2.8 Å and a separation between the two minima of 0.8 Å has been found in the paramagnetic phase. The apparent central position of the muon seems to be the result of fast muon tunneling between two equivalent minima in the F--μ+--F bond. [ABSTRACT FROM AUTHOR]

Muon spin rotation (µSR) and relaxation has been used to study the local magnetic structure of K3Fe5F15. A collinear F-µ+-F "hydrogen bond-like" symmetric double minimum type complex with a F...F distance of 2.8 Å and a separation between the two minima of 0.8 Å has been found in the paramagnetic phase. The apparent central position of the muon seems to be the result of fast muon tunneling between two equivalent minima in the F-µ+-F bond.