Water spectra permanent dipole

It is plausible that the RF-backbone of the aerogels alone shows no resonant polarization in the frequency-band investigated. The molecules have no permanent dipole moment which could oscillate at these frequencies. All other possible relaxation phenomena (e.g. vibrational or electronic polarization) take place in frequency bands well above the one investigated. From results 8.3. we learn, that water has a strong influence on the impedance spectrum and thus on the relaxation, e" increases while the characteristic frequency (Uioss decreases with the amount of water adsorbed. 

The LIB fraction (the fraction of monomers) containing about 55-70% of all water molecules comprises a permanent dipole, namely, a neutral molecule librating in a tight surrounding of other molecules in a condensed medium. This motion, governed by mechanism a, is responsible for the librational band, placed near the boundary of the IR region, and for the low-frequency Debye relaxation band, placed at microwaves. The Debye spectrum is not considered in this work. 

The hat model also describes the low-frequency (Debye) spectrum of water placed at the frequency v about 10cm 1. The ice spectrum is characterized by quite other behavior. In this frequency range we see no signs of mechanism a pertaining to libration of a permanent dipole in a certain intermolecular well. 

In the far-infrared spectral region water vapour can absorb radiation by transition between different rotational levels without any vibrational or electronic changes. Such a pure rotational spectrum can only be exhibited by a molecule with a permanent dipole moment. The rotational spectrum has been measured for wavelengths up to 2 mm(Herzberg, 1945, p. 58 Furashov, 1966), where this type of absorption ceases and, in good agreement with theory, consists of relatively sharp lines distributed in what looks... 

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