Vibrational bands of water

Cu Y. The absorption spectra of hydrated and dehydrated CuIJY zeolites are shown in Figs. 5 and 6, respectively. The dehydrated Cu Y zeolite also displayed a weak photoluminescence at 540 nm, in qualitative accord with the reports of partial autoreduction of Cu to Cu upon dehydration, which amounts to approximately 20% of Cu converted to Cu at the dehydration temperature of 400°C (3). The sharp peaks at 5200 and 7000 cm- in Fig. 5 are the (v+6) and (2v) vibrational bands of water (14). Their absence in Fig. 6 demonstrates that the dehydration of Cu Y is complete. Also, absence of the silanol (2v) band at 7300 cm- (I5) shows that hydroxyl groups are absent in the dehydrated Cu Y as well as in all subsequently treated copper zeolites. The broader bands between 9000 and 16000 cm and above 30000 cm- are electronic absorption spectra of the copper species in the hydrated and dehydrated Cu Y, as follows from their comparison with the spectra of NaY and CuxY. 

Noncontact-type heating allows heat transfer by noncontacting methods to fluids such as radiative and ultrasonic heating. Infrared temperature control [4] is a noncontact heating technique, which uses the infrared excitation of a vibration band of water combined with a high-power halogen light bulb and an optical Alter (Fig. 2). 

Vibrational Modes of Water Molecules in Solid Hydrates -Intermolecular Coupling and Correlation Field Splitting of the Water Bands... 

The difficulties in interpreting the vibrational spectrum of water are obvious. Because of the broad nature of the bands, the two stretching modes Vj and V3 overlap. In addition, overtones complicate the assignment of bands. Thus, the first overtone of the V2 bending mode, 2v2, lies close in frequency to the stretching modes Vj and V3. For these reasons, there are advantages in studying HOD, a molecule for which the vibrational frequencies are quite different. As a result,... 

Time-resolved nonlinear IR spectroscopy is a modem version of ordinary IR spectroscopy examined above. It has been referred to all along the preceding chapters. In Ch. 4 it has been shown to convey information on the dynamics of the surrounding of the studied vibration, in addition to information on this vibration itself, which is the main type of information conveyed by ordinary IR spectroscopy, also named ID IR. This supplementary information appears through the measurements of the lifetime or relaxation time of the studied vibration. Most results obtained up to now with such methods concern liquid water. They have been described in Ch. 4, because they may be applied to any H-bonded system. They have given values of relaxation times of bands of water molecules in liquid water and have thus shown a marked isotopic dependence. Thus the relaxation time of... 

In the near infrared, the absorption of solar radiation is due chiefly to vibrational and rotational transitions of several atmospheric molecules. The most important absorber is water vapor with several absorbing bands between 0.8 and 3.2 gm. Carbon dioxide also exhibits absorption bands such as the 2.0 gm band, the 2.7 /.tin band (which overlaps with the 2.7 /nn band of water vapor) and the 4.3 /.tin band, located in a spectral region where both solar and terrestrial radiation is weak. Since these bands consist of many narrow lines, the transmission function corresponding to a given spectral interval cannot be described in terms of the Beer-Lambert law and empirical formulas must be used in practical applications. 

Water is dominant in the IR spectrum of swollen hydrogels. Figure 19a shows the ATR spectrum of water-containing PVP. The three strongest absorption bands are due to vibrational modes of water. The weak bands that are indicated by a star in Fig. 19a arise from PVP. The Raman spectrum of the same sample is represented in... 

The S-H vibration in proteins has been studied by Yu et and Li et alP This vibration, which occurs in the range of 2500-2600 cm, is far from any other Raman bands including the librational bands of water that extend from less than 1 cm to about 1750 cm . This permits one to observe the S-H vibration in proteins even though the concentration of the -SH group is very low and there is no resonance enhancement. (Sometimes, however, fluorescence may be a problem.) Yu et have studied the disappearance of the S-H vibration in lens on aging that is caused by the oxidation of the -SH groups to disulfide (—S—S—) groups. Li et have studied the effect of the environment on the frequencies... 

It is generally accepted that hydroxyl groups of dehydrated silica surface are the main sites of adsorption of the molecules capable to form hydrogen bonds with these sites (water, alcohol, amines). This conclusion was made on the base of investigation of the shift of vibration bands of free Si—OH groups to low frequency region [49,50]. The following models are proposed, for example, for the adsorption complexes of water on silica surface ... 

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