Chapter 3. Low-frequency spectroscopic studies and intermolecular vibrational energy transfer in liquids

Nielsen, O. Faurskov

doi:10.1039/pc093057

Cited by 47 publications

(13 citation statements)

References 224 publications

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“…[22][23][24][25] At low temperatures the absorption lines are very well developed in beryl because the water molecules are confined to a clearly defined and highly symmetric crystalline environment. Our experiments evidence that they do not involve large H 2 O molecular complexes, as it is suggested for liquid water or in ice [20][21][22][23][24][25] , and are of extreme local character, i.e. just a single H 2 O molecule is involved, in agreement with simulations 22,26 and experiments on aqueous solutions.…”

supporting

confidence: 90%

“…Their nature can be assigned to the response of type-II water molecules, whose stronger coupling to the cations (compared to type-I molecules that are H-bonded to the cage walls) leads to significantly different characteristics of the resonances, namely smaller damping and spectral weight. Another explanation is based on the observation of similar resonance absorptions around 50 -60 cm -1 in liquid water and ice; [18][19][20][21] they might be connected to the bending of the H-bonds, but this is still under debate. [22][23][24][25] At low temperatures the absorption lines are very well developed in beryl because the water molecules are confined to a clearly defined and highly symmetric crystalline environment.…”

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confidence: 99%

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Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstones

Gorshunov

Жукова

Torgashev

et al. 2013

J. Phys. Chem. Lett.

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When water is confined to nanocavities, its quantum mechanical behavior can be revealed by terahertz spectroscopy. We place H2O molecules in the nanopores of a beryl crystal lattice and observe a rich and highly anisotropic set of absorption lines in the terahertz spectral range. Two bands can be identified, which originate from translational and librational motions of the water molecule isolated within the cage; they correspond to the analogous broad bands in liquid water and ice. In the present case of well-defined and highly symmetric nanocavities, the observed fine structure can be explained by macroscopic tunneling of the H2O molecules within a six-fold potential caused by the interaction of the molecule with the cavity walls.

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confidence: 90%

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confidence: 99%

Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstones

Gorshunov

Жукова

Torgashev

et al. 2013

J. Phys. Chem. Lett.

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“…A band around 190 cm -1 is also seen in pure water and is moderately intense but slightly polarized. This band has been assigned as a restricted translation mode of the H-bonded water molecules, and the band is anion and concentration dependent (refs , ). In concentrated Mg(ClO 4 ) 2 solutions other H-bonds are important, namely, OH···OCl .…”

Section: Resultsmentioning

confidence: 99%

“…In addition to theoretical methods, Raman spectroscopy has been extensively used to elucidate the spectroscopic characteristics of hydrated cations in aqueous solutions. However the strong quasi-elastic Rayleigh wing, extending over 500 cm -1 , prohibits the clear detection of the weak low-frequency modes of the metal aquo ions. , Although difference spectroscopy or the subtraction of a synthetic background can be employed, the fact that anions alter the low-frequency Raman spectrum of water places some doubt on the validity of the subtraction procedure, as previously pointed out. − The use of reduced spectra, constructed by normalizing the low-frequency Raman data for the Bose−Einstein temperature factor ( B ) and a frequency factor, as in eq 1, gives accurate relative intensity data. , …”

Section: Introductionmentioning

confidence: 99%

An ab Initio and Raman Investigation of Magnesium(II) Hydration

1998

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The weak polarized Raman band assigned to the ν1-MgO6 mode of the hexaaquo Mg(II) ion has been studied over the temperature range 25 to 125 °C. The 356 cm-1 stretching mode frequency decreases by about 3 cm-1 but broadens by 13 cm-1 over a 100 °C temperature range. A depolarized mode at 235 cm-1 could be assigned to ν2. These data suggest that the hexaaquo Mg(II) ion is thermodynamically stable in perchlorate and chloride solutions. In sulfate solutions, an equilibrium exists between the hexaaquo ion and an inner-sphere sulfato complex. Ab initio geometry optimizations of Mg(H2O)6 2+ were carried out at the Hartree−Fock and Møller−Plesset levels of theory, using various basis sets up to 6-31+G*. Frequency calculations confirm that the T h structure is a minimum. The unscaled frequencies of the MgO6 unit are lower than the experimental frequencies, and scaling only marginally improves the agreement. The theoretical binding enthalpy for the hexaaquo Mg(II) ion accounts for about 70% of the experimental hydration energy of Mg(II). A comparison of three models for the second hydration sphere is presented, and the most suitable is found to be one of lower symmetry T, in which alternate faces of the MgO6 octahedron are H-bonded to water trimers. The unscaled Hartree−Fock frequencies agree very well with our experimental observations, giving nearly exact agreement with experiment.

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“…The intensity of this band at 170 cm −1 is linked to the damped stretching intermolecular modes of hydrogen bonded species and is sensitive to different structures of water [ 34 , 35 , 36 ]. The change in the intensity of the 170 cm −1 feature with initial increase in NaCl concentration is associated with enhanced water structuring and increased tetrahedral ordering of water [ 37 , 38 , 39 ]. From a microstructural perspective, this change may be attributed to an increase in the number of bound water molecules as the micelles grow from spherical to cylindrical.…”

Section: Resultsmentioning

confidence: 99%

Revealing New Structural Insights from Surfactant Micelles through DLS, Microrheology and Raman Spectroscopy

Amin¹,

Blake²,

Kennel

et al. 2015

Materials

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The correlation between molecular changes and microstructural evolution of rheological properties has been demonstrated for the first time in a mixed anionic/zwitterionic surfactant-based wormlike micellar system. Utilizing a novel combination of DLS-microrheology and Raman Spectroscopy, the effect of electrostatic screening on these properties of anionic (SLES) and zwitterionic (CapB) surfactant mixtures was studied by modulating the NaCl concentration. As Raman Spectroscopy delivers information about the molecular structure and DLS-microrheology characterizes viscoelastic properties, the combination of data delivered allows for a deeper understanding of the molecular changes underlying the viscoelastic ones. The high frequency viscoelastic response obtained through DLS-microrheology has shown the persistence of the Maxwell fluid response for low viscosity solutions at high NaCl concentrations. The intensity of the Raman band at 170 cm−1 exhibits very strong correlation with the viscosity variation. As this Raman band is assigned to hydrogen bonding, its variation with NaCl concentration additionally indicates differences in water structuring due to potential microstructural differences at low and high NaCl concentrations. The microstructural differences at low and high NaCl concentrations are further corroborated by persistence of a slow mode at the higher NaCl concentrations as seen through DLS measurements. The study illustrates the utility of the combined DLS, DLS-optical microrheology and Raman Spectroscopy in providing new molecular structural insights into the self-assembly process in complex fluids.

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Chapter 3. Low-frequency spectroscopic studies and intermolecular vibrational energy transfer in liquids

Cited by 47 publications

References 224 publications

Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstones

Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstones

An ab Initio and Raman Investigation of Magnesium(II) Hydration

Revealing New Structural Insights from Surfactant Micelles through DLS, Microrheology and Raman Spectroscopy

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