Water spectra frequency ranges

Specific gravity—The weight of a material compared to the weight of an equal volume of water. Spectrum— A range of freqnencies within which radiation has some specified characteristic, such as audio-frequency spectrum, ultraviolet spectrum, and radio spectrum. 

In Section V the reorientation mechanism (A) was investigated in terms of the only (hat curved) potential well. Correspondingly, the only stochastic process characterized by the Debye relaxation time rD was discussed there. This restriction has led to a poor description of the submillimeter (10-100 cm-1) spectrum of water, since it is the second stochastic process which determines the frequency dependence (v) in this frequency range. The specific vibration mechanism (B) is applied for investigation of the submillimetre and the far-infrared spectrum in water. Here we shall demonstrate that if the harmonic oscillator model is applied, the small isotope shift of the R-band could be interpreted as a result of a small difference of the masses of the water isotopes. 

Hindered rotations (librational modes) of a rigid water molecule in ice are observed in the frequency range of 600-900cm In Ih phase, as shown in the top of Fig. 5, weak and broad peaks are observed at about 770cm and 910cm" (shown by arrows) and the spectra show almost no polarization dependence. In addition to these peaks, a step-wise jump is seen at 1080cm and it becomes more clear in c(a,a)b spectrum in XI phase, the origin of which has not been known yet. 

Rast et al. studied the mechanisms of the intermolecular NMR relaxation dispersion of the tetramethylammonium protons in Gd " heavy-water solutions. The standard dipolar nuclear relaxation formalism of Solomon-Bloembergen, valid for the used frequency range between 10 and 800 MHz, leads to overall good agreement with the measured data without any adjustable parameters. Madhu et al. reported experimental observation and numerical simulation of a two-dimensional multiplet effect in the heteronuclear correlation spectrum of a paramagnetic protein that depends on molecular geometry. Bertini et performed solution structure calculations through self-... 

Fig. 5.14 Infrared spectrum of purified water in the frequency range 4000-400 cm. (From reference 26, with permission.)...

We remark that in simple liquids only one band arises, usually centered at several hundredths of cm-1. On the contrary, the water spectrum, which covers up to 1000 cm-1, is two-humped. Its high-frequency part, bordering with the IR range, is to a certain extent similar to the spectrum of simple polar liquids, while a specific low-frequency part, with the absorption maximum near 200 cm-1, is typical of water/ice. The latter maximum, arising undoubtedly due to the existence of hydrogen bonds (HB), is lacking in simple liquids. 

In this section we calculate the water spectrum in the range 0-1000 cm-1. This calculation is based on an analytical theory elaborated in 2005-2006 with the addition of a new criterion (38), related to the 50-cm 1 band in the low-frequency Raman spectrum. The calculation scheme was briefly described in Section II. One of our goals is to compare the spectra of liquid H20 and D20 and the relevant parameters of the model. Particularly, we consider the isotopic shift of the complex permittivity/absorption spectra and the terahertz (THz) spectra of both fluids. Additionally, in Appendix II we take into account the coupling of two modes, pertinent to elastically vibrating HB molecules. 

The model described in this chapter can be applied to the calculation of the permittivity spectra in water in the broad frequency range 0-1000 cm-1 and to calculation of the ice far-IR spectra in the resonance region 50-1000 cm-1. As seen in Fig. 26 (curves I), in a nonresonance ice spectrum only the transverse-vibration mechanism (d) works. Indeed, we see from Fig. 24b that at v < 50 cm-1, namely in the submillimeter wavelength region and at lower frequencies, mechanisms a-c practically vanish. 

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 Figure 2b we observe that in the frequency range between 3-750 Hz, the spectra exhibit rapid oscillations. This part of the spectra captures the slow P-wave motion due to propagation of a pulse in the fluid (water) of the aquifer when the matrix is relaxed (or in state of equilibrium). Oscillations in the spectrum arise from phase differences in the slow and fast waves. As seen in Figure 2b, these rapid oscillations occur for each of the pressure peaks. This suggests that the slow wave can be excited at frequencies equal to or less than the mesocopic frequency. 

Since the volume fractions of free, cpf, and bound, cp, water are both unknown, it is convenient to measure the dielectric permittivity in a frequency range where the dielectric loss of bound water may be safely neglected. The relaxation spectrum of free and bound water for our systems will safely satisfy this requirement at the measurement frequency of 75 GHz. In this case, die complex permittivity of the bound water is equal to its real part, i.e., = s -i-... 

Attenuation spectra measured in the first run up to if = 80 are presented in Fig. 13. The results for if = 90 and R = 100 are not reported because fliey were found to vary appreciably. As the water concentration is increased, the attenuation spectrum rises in intensity and there is a distinct jump in the attenuation spectrum from if = 5- to if = 60 in the low-frequency range. This discontinuity is also reflected in the visual appearance, as at if = 60 the system becomes turbid. The smooth shape of the attenuation curve also... 

Many other interaction energies come from the electromagnetic frequency spectrum. They can come from outside of the ultraviolet, visible, and infrared frequency ranges. All that is required is an element of the model protein in water that is able to take up the energy. The dipole moment of the peptide group with its positive end at the NH and its negative end at the oxygen of the CO provides one site of inter-... 

Morita and Hynes S have attempted an analysis of the sum frequency generation spectrum at the surface of water from ab initio calculations of normal mode shifts and hyperpolarizability in the frequency range of the OH stretch. Molecular dynamics has been used to generate a sample of structures. Agreement between the simulated and experimental spectra is good. The spectrum appears to depend on signals from molecules in a few standard orientations in the top two layers at the surface. 

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