Raman scattering of water

Chen, Y. X. and Tian, Z. Q. (1997) Dependence of surface enhanced Raman scattering of water on the hydrogen evolution reaction. Chem. Phys. Lett., 281, 379-383. 

The Raman scattering of water serves as a sensitivity test for fluorometers. This consists of measuring the signal/noise ratio of the Raman peak with a cell filled with water, for example at 397 nm if the excitation wavelength is fixed at 350 nm, as a result of the specific shift of 3380 cm for this solvent, and to compare with the background signal. 

Apart from the narrow Raman scatter of water at 310nm, the fluorescence spectrum showed a single broad band peak at 460 nm, and should be perceived as an average fluorescent signature of the humic substances in accordance with their composite nature. 

The "transparency" of water and glass the very low Raman scattering of water (which is important for living systems) and of glass make it suitable for dilute aqueous solutions of substances as well as for hygroscopic materials, and permits the use of standard glass cuvettes and capillaries. 

Kwon, M.Y. and Kim, J.J. (1990) Surface-enhanced Raman scattering of water in ethanol Electrolytic concentration dependence. Chemical Physics Letters, 169, 337-341. 

Raman spectroscopy is complementary to IR and due to differences in the nature of the selection rules yields vibrational information not obtainable from IR. In many cases, Raman spectroscopy is particularly useful when ease of sampling and remote sampling is important. Raman also is advantageous in aqueous solution due to low Raman scattering of water. On the other hand, Raman has been utilized more as a research tool than an analytical tool for polymers. The basic reason for this practical limitation is the ubiquitous fluorescence which occurs with polymers. However, in recent years, tremendous progress has been made and Raman is becoming a more common tool for polymer analysis. 

With the microfocus instrument it is possible to combine the weak Raman scattering of liquid water with a water-immersion lens on the microscope and to determine spectra on precipitates in equilibrium with the mother liquor. Unique among characterization tools, Raman spectroscopy will give structural information on solids that are otherwise unstable when removed from their solutions. 

Effect of Underpotentially Deposited Lead on the Surface-Enhanced Raman Scattering of Interfacial Water at Silver Electrode Surfaces... 

Raman scattering in water is used as a sensitivity test for fluorimeters. The test consists of measuring the signal to noise ratio of the Raman peak using a cell filled with water. For example, signal/noise will be measured at 397 nm (25191 cm1) if the excitation energy used is 350 nm (28571 cm 1). 

When an electron is injected into a polar solvent such as water or alcohols, the electron is solvated and forms so-called the solvated electron. This solvated electron is considered the most basic anionic species in solutions and it has been extensively studied by variety of experimental and theoretical methods. Especially, the solvated electron in water (the hydrated electron) has been attracting much interest in wide fields because of its fundamental importance. It is well-known that the solvated electron in water exhibits a very broad absorption band peaked around 720 nm. This broad absorption is mainly attributed to the s- p transition of the electron in a solvent cavity. Recently, we measured picosecond time-resolved Raman scattering from water under the resonance condition with the s- p transition of the solvated electron, and found that strong transient Raman bands appeared in accordance with the generation of the solvated electron [1]. It was concluded that the observed transient Raman scattering was due to the water molecules that directly interact with the electron in the first solvation shell. Similar results were also obtained by a nanosecond Raman study [2]. This finding implies that we are now able to study the solvated electron by using vibrational spectroscopy. In this paper, we describe new information about the ultrafast dynamics of the solvated electron in water, which are obtained by time-resolved resonance Raman spectroscopy. 

Visible or near-IR lasers are normally used and since water is transparent in this region, biological samples can be examined directly. It further helps that Raman scattering from water (unlike IR absorbance) is relatively weak. Examples of Raman spectra are shown in Figures 2.34 and 2.35. 

Raman spectroscopy is useful for studying aqueous solutions, e.g., of polymers, because the spectra are hardly affected by the presence of water. The two major problems of the technique are (1) the low intensities of the Stokes lines (hence data acquisition is slow), and (2) laser-induced fluorescence effects, which may be so intense that they can completely wipe out all Raman scattering of interest. 

These three configuration possibilities do not, of course, pass into one another at sharp transition points, as would be expected in the case of crystalline phases rather, they resolve into one another gradually with increasing temperature. The fact that the Raman spectrum of water undergoes a very considerable modification with temperature is in harmony with this view. Moreover, a mixture of quartz-like tetrahedral structure and close packing approximates very closely to the scattering curve determined experimentally at 20 , as seen in Fig. 63. 

Nonlinear optical interactions in micrometer-size liquid droplets are readily observable. New data on the stimulated Raman scattering of benzene droplets (up to the 6th-order Stokes), and water droplets containing KNO ... 

Figure 9 The dashed curve is the fluorescence spectrum of a protein sample with = 290 nm. The solid curve with circles is the spectrum of the buffer blank, showing a maximum signal at 321 nm, corresponding to the Raman scatter of the water. The solid curve is the signal resulting from subtracting the buffer blank from the raw spectral data.

The weak Raman scattering from water allows the direct observation of the oxide species in the aqueous phase, the nanocrystalline nucleation seeds, and the solid phases present during zeolite synthesis, which are not as readily detectable with x-ray diffraction (XRD). The transformation of aluminosilicate gel to zeolite A was investigated with Raman spectroscopy by several researchers [150,179,180], but one outstanding investigation also... 

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