Raman water

A method which has been developed to circumvent the lack of understanding physical processes in remote Chi sensing is the normalization of fluorescence signals by the Raman water OH stretch signal occurring at a frequency shift of 3418 cm [8]. Nearly linear relationships between normalized fluorescence and in situ Chi concentration (0.2-20 pg L ) were observed by Brislow et al. [10] with 470-nm excitation and by Hoge and Swift [11] with 532-nm excitation. 

Fluorescence is an extremely sensitive technique but it is not suitable as a general method to estimate natural DOC content due to the reason that it is impossible to find a reference material that would be common for all different natural waters. Characteristic for different fluorescence studies of NOM/DOM is that they may occasionally be somewhat surprising, contradictory, or laboriously explicable. The main reason for this incoherence is that fluorescence measurements are affected by many environmental factors, e.g., type of solution, pH, ionic strength, temperature, redox potential of the medium, and interactions with metal ions and organics. Several corrections are required to obtain a reliable and comparable spectrum, e.g., instrumental factors, Raman water peak, scattering effects (primary and secondary inner filter effects [31,32]), arbitrary fluorescence units should be standardized (dihydrate of quinine sulfate), etc. 

The varying actual orientation of molecules adsorbed at an aqueous solution-CCU interface with decreasing A has been followed by resonance Raman spectroscopy using polarized light [130]. The effect of pressure has been studied for fatty alcohols at the water-hexane [131] and water-paraffin oil [132] interfaces. 

Fig. IV-14. Resonance Raman Spectra for cetyl orange using 457.9-nm excitation. [From T. Takenaka and H. Fukuzaki, Resonance Raman Spectra of Insoluble Monolayers Spread on a Water Surface, J. Raman Spectr., 8, 151 (1979) (Ref. 157). Copyright Heyden and Son, Ltd., 1979 reprinted by permission of John Wiley and Sons, Ltd.]...

The behavior of insoluble monolayers at the hydrocarbon-water interface has been studied to some extent. In general, a values for straight-chain acids and alcohols are greater at a given film pressure than if spread at the water-air interface. This is perhaps to be expected since the nonpolar phase should tend to reduce the cohesion between the hydrocarbon tails. See Ref. 91 for early reviews. Takenaka [92] has reported polarized resonance Raman spectra for an azo dye monolayer at the CCl4-water interface some conclusions as to orientation were possible. A mean-held theory based on Lennard-Jones potentials has been used to model an amphiphile at an oil-water interface one conclusion was that the depth of the interfacial region can be relatively large [93]. 

One of the well known advantages of resonance Raman spectroscopy is that samples dissolved in water can be studied since water is transparent in the visible region. Furthennore, many molecules of biophysical interest assume their native state in water. For this reason, resonance Raman spectroscopy has been particularly strongly embraced in the biophysical connnunity. 

Undeniably, one of the most important teclmological achievements in the last half of this century is the microelectronics industry, the computer being one of its outstanding products. Essential to current and fiiture advances is the quality of the semiconductor materials used to construct vital electronic components. For example, ultra-clean silicon wafers are needed. Raman spectroscopy contributes to this task as a monitor, in real time, of the composition of the standard SC-1 cleaning solution (a mixture of water, H2O2 and NH OH) [175] that is essential to preparing the ultra-clean wafers. 

Plenary 3. Ronald E Hester et al, e-mail address reh York.ac.uk (SERS). Use of dioxane envelope to bring water insoluble cliromophores (chlorophylls) into contact with aqueous silver colloids for SERS enliancement. PSERRS— protected surface-enhanced resonance Raman spectroscopy . 

Plenary 8. J Grave et al, e-mail address J.Greve tn.utwente.nl (RS). Confocal direct unaging Raman microscope (CDIRM) for probing of the human eye lens. High spatial resolution of the distribution of water and cholesterol in lenses. 

Walrafen G E 1967 Raman spectral studies of the effects of temperature on water structure J. Chem. Phys. 47 114-26... 

De Santis A, Sampoli M, Mazzacurati V and Ricci M A 1987 Raman spectra of water in the translational region Chem. Phys. Lett. 133 381-4... 

Nardone M, Ricci M A and Benassi P 1992 Brillouin and Raman scattering from liquid water J. Mol. 

Carey D M and Korenowski G M 1998 Measurement of the Raman spectrum of liquid water J. Chem. Phys. 108 2669-75... 

The state of aqueous solutions of nitric acid In strongly acidic solutions water is a weaker base than its behaviour in dilute solutions would predict, for it is almost unprotonated in concentrated nitric acid, and only partially protonated in concentrated sulphuric acid. The addition of water to nitric acid affects the equilibrium leading to the formation of the nitronium and nitrate ions ( 2.2.1). The intensity of the peak in the Raman spectrum associated with the nitronium ion decreases with the progressive addition of water, and the peak is absent from the spectrum of solutions containing more than about 5% of water a similar effect has been observed in the infra-red spectrum. ... 

In equimolar mixtures of nitric acid and water a monohydrate is formed whose Raman spectrum has been observed. There is no evidence for the existence of appreciable concentrations of the nitric acidium ion in aqueous nitric acid. 

Raman spectroscopy I c.i.so showed that the addition of up to io% of water does not affect the concentration of nitronium ions further dilution reduces the concentration of this species, which is not detectable in solutions containing < 85 % sulphuric acid. The introduction of... 

Solutions of dinitrogen pentoxide in nitric acid or sulphuric acid exhibit absorptions in the Raman spectrum at 1050 and 1400 cm with intensities proportional to the stoichiometric concentration of dinitrogen pentoxide, showing that in these media the ionization of dinitrogen pentoxide is complete. Concentrated solutions in water (mole fraction of NgOg > 0-5) show some ionization to nitrate and nitronium ion. Dinitrogen pentoxide is not ionized in solutions in carbon tetrachloride, chloroform or nitromethane. ... 

Table 1 Hsts some of the physical properties of duoroboric acid. It is a strong acid in water, equal to most mineral acids in strength and has a p p o of —4.9 as compared to —4.3 for nitric acid (9). The duoroborate ion contains a neady tetrahedral boron atom with almost equidistant B—F bonds in the sohd state. Although lattice effects and hydrogen bonding distort the ion, the average B—F distance is 0.138 nm the F—B—F angles are neady the theoretical 109° (10,11). Raman spectra on molten, ie, Hquid NaBF agree with the symmetrical tetrahedral stmcture (12).

Lead Telluride. Lead teUuride [1314-91 -6] PbTe, forms white cubic crystals, mol wt 334.79, sp gr 8.16, and has a hardness of 3 on the Mohs scale. It is very slightly soluble in water, melts at 917°C, and is prepared by melting lead and tellurium together. Lead teUuride has semiconductive and photoconductive properties. It is used in pyrometry, in heat-sensing instmments such as bolometers and infrared spectroscopes (see Infrared technology AND RAMAN SPECTROSCOPY), and in thermoelectric elements to convert heat directly to electricity (33,34,83). Lead teUuride is also used in catalysts for oxygen reduction in fuel ceUs (qv) (84), as cathodes in primary batteries with lithium anodes (85), in electrical contacts for vacuum switches (86), in lead-ion selective electrodes (87), in tunable lasers (qv) (88), and in thermistors (89). 

Principal component analysis has been used in combination with spectroscopy in other types of multicomponent analyses. For example, compatible and incompatible blends of polyphenzlene oxides and polystyrene were distinguished using Fourier-transform-infrared spectra (59). Raman spectra of sulfuric acid/water mixtures were used in conjunction with principal component analysis to identify different ions, compositions, and hydrates (60). The identity and number of species present in binary and tertiary mixtures of polycycHc aromatic hydrocarbons were deterrnined using fluorescence spectra (61). 

Coumaria is usually sold in the form of colorless shiny leaflets or rhombic crystals. Its ir (7), uv (8), Raman (9), and nmr spectra (10) are known. Physical constants appear ia Table 1. Tables 2 and 3 give the solubiUty of coumaria ia various water mixtures and solvents. 

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. 

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