Indirect relaxation, hydrogen bonds

Relaxation and self-diffusion techniques in solution are widely used to study hydrogen-bonded systems. The nuclear quadrupole coupling constant (NQCC) presents a sensitive probe for the strength of hydrogen bonding. Unfortunately in the liquid phase this property cannot be measured in a direct way. Two new indirect methods are now presented for determining NQCC in H-bonded liquids. Ferris and Farrar showed that for the OD deuteron of ethanol the DQCC is related to the chemical shift of the hydroxy proton by a linear equation. Thus the straightforward measurement of the chemical shift... 

The information presented in Sections 5.1.1.1-5.1.1.4 and Table 5.1, although construed to pertain to the effects of ions on the structure of the solvent, in the sense of whether it is enhanced or loosened by the presence of ions, actually reflects the effects on the dynamics of the solvent in the immediate neighborhood of the ions. The mean residence times of water molecules in the vicinity of ions are indirectly measures of the effect of the ions on the structure of the water as described in Section 5.2.1. There are aspects of solvent dynamics that are not covered by these effects, such as the orientational relaxation rate and hydrogen-bond lifetimes. Two experimental methods have mainly been employed for obtaining such information ultrafast mid-infrared and dielectric relaxation spectroscopy on the fs to ps time scales. Some slower processes were studied by NMR relaxation studies. Computer simulations added additional information, since it could be applied to individual ions rather than salts. As for the ion effects dealt with in the previous sections, the vast majority of the studies dealt with ions in aqueous solutions and only few ones considered ions in nonaqueous solvents... 

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