85 research outputs found
Glasslike Behavior in Aqueous Electrolyte Solutions
When salts are added to water, the viscosity generally increases suggesting
the ions increase the strength of the water's hydrogen-bond network. However,
infrared pump-probe measurements on electrolyte solutions have found that ions
have no influence on the rotational dynamics of water molecules implying no
enhance-ment or breakdown of the hydrogen-bond network. Here we report optical
Kerr-effect and dielectric relaxa-tion spectroscopic measurements, which have
enabled us to separate the effects of rotational and transitional motions of
the water molecules. These data show that electrolyte solutions behave like a
supercooled liquid approaching a glass transition in which rotational and
translational molecular motions are decoupled. It is now possible to understand
previously conflicting viscosity data, nuclear magnetic resonance relaxation,
and ultrafast infrared spectroscopy in a single unified picture
Structure and dynamics in protic ionic liquids: a combined optical Kerr-effect and dielectric relaxation spectroscopy study
The structure and dynamics of ionic liquids (ILs) are unusual due to the strong interactions between the ions and counter ions. These microscopic properties determine the bulk transport properties critical to applications of ILs such as advanced fuel cells. The terahertz dynamics and slower relaxations of simple alkylammonium nitrate protic ionic liquids (PILs) are here studied using femtosecond optical Kerr-effect spectroscopy, dielectric relaxation spectroscopy, and terahertz time-domain spectroscopy. The observed dynamics give insight into more general liquid behaviour while comparison with glass-forming liquids reveals an underlying power-law decay and relaxation rates suggest supramolecular structure and nanoscale segregation
Chemical data evaluation: General considerations and approaches for IUPAC projects and the chemistry community (IUPAC Technical Report)
The International Union of Pure and Applied Chemistry has a long tradition of supporting the
compilation of chemical data and their evaluation through direct projects, nomenclature and terminology
work, and partnerships with international scientific bodies, government agencies, and other organizations.
The IUPAC Interdivisional Subcommittee on Critical Evaluation of Data has been established to provide
guidance on issues related to the evaluation of chemical data. In this first report, we define the general
principles of the evaluation of scientific data and describe best practices and approaches to data evaluation in
chemistryinfo:eu-repo/semantics/publishedVersio
Systematic Variations of Ion Hydration in Aqueous Alkali Metal Fluoride Solutions
Aqueous solutions of three alkali metal fluorides-NaF, KF, and CsF-have been studied by dielectric relaxation spectroscopy (DRS) over the frequency range 0.2 less than or similar to nu/GHz > Na+ > K+ > Rb+ > Cs+. It was also found that Z(s)(0)(M'(+)), the number of moderately bound ("slow") water molecules, varied in the same order: K+ > Rb+ > Cs+. However, the presence of ib water molecules in the hydration shells of Li+ and Na+ attenuates their further interaction with surrounding water molecules such that Z(s)(0)(M'(+)) approximate to 0 for both ions
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