| Autor: |
B.M. Tseitlin, Vladimir I. Gaiduk, Derrick Crothers |
| Rok vydání: |
2005 |
| Předmět: |
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| Zdroj: |
Journal of Molecular Structure. 738:117-127 |
| ISSN: |
0022-2860 |
| Popis: |
Wideband far infrared (FIR) spectra of complex permittivity e ( ν ) of ice are calculated in terms of a simple analytical theory based on the method of dipolar autocorrelation functions. The molecular model represents a revision of the model recently presented for liquid water in Adv. Chem. Phys. 127 (2003) 65. A composite two-fractional model is proposed. The model is characterised by three phenomenological potential wells corresponding to the three FIR bands observed in ice. The first fraction comprises dipoles reorienting in a rather narrow and deep hat-like well; these dipoles generate the librational band centred at the frequency ≈880 cm −1 . The second fraction comprises elastically interacting particles; they generate two nearby bands placed around frequency 200 cm −1 . For description of one of these bands the harmonic oscillator (HO) model is used, in which translational oscillations of two charged molecules along the H-bond are considered. The other band is produced by the H-bond stretch, which governs hindered rotation of a rigid dipole. Such a motion and its dielectric response are described in terms of a new cut parabolic (CP) model applicable for any vibration amplitude. The composite hat-HO–CP model results in a smooth e ( ν ) ice spectrum, which does not resemble the noise-like spectra of ice met in the known literature. The proposed theory satisfactorily agrees with the experimental ice spectrum measured at −7 °C. The calculated longitudinal optic-transverse optic (LO–TO) splitting occurring at ≈250 cm −1 qualitatively agrees with the measured data. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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