Ultraviolet-Visible-Near Infrared concentration

Figure 18-6 (a) Absorption spectrum of KMnO at four different concentrations, (b) Peak absorbance at 555 nm is proportional to concentration from 0.6 xM to 3 mM. The Cary 5000 ultraviolet-visible-near infrared spectrophotometer used for this work has a wider operating range than many instruments. It is difficult to measure absorbance accurately above 2 or below 0.01. [From A. R. Hind, Am. Lab., December 2002, p. 32. Courtesy Varian, Inc., Palo Alto, CA.]... 

Recently was estimated an expected impact on the global chemistry of the atmosphere of the indirect heterogeneous photocatalytic reactions under the much more abundant near ultraviolet, visible and near infrared solar light [2]. As photocatalysts may serve atmospheric aerosols, i.e. ultrasmall solid particles that sometimes are embedded into liquid droplets. Aerosols are known to contain Ti02, Fc203, ZnO and other natural oxides, as well as metal sulfides of volcanic or antropogenic origin, that may serve as semiconductor photocatalysts (see Fig.5). Aerosols are known to be concentrated mainly in the air layers near the surface of the Earth, i.e. in the troposphere, rather than stratosphere. 

Laser Ocular Biology. The biological effects of laser radiation on the eyes vary with the laser wavelength, pulse duration, and intensity. The cornea and lens focuses visible and near-infrared laser radiation onto the retina where the concentrated energy directly impacts the photoreceptor cells and supporting tissue. The cornea and lens absorb ultraviolet and mid-to-far-infrared laser radiation. Alteration can occur in these tissues, but the retina will be spared. 

Spectroscopic methods are also commonly used for the analysis of surfactants. Among these methods ultraviolet/visible spectrophotometry and infrared/near-infrared spectroscopy are used for the measurement of surfactant concentration, while such techniques as nuclear magnetic resonance (NMR) and mass-spectroscopy (MS) are extensively used for... 

Raman spectroscopy is a vibrational spectroscopic technique which can be a useful probe of protein structure, since both intensity and frequency of vibrational motions of the amino acid side chains or polypeptide backbone are sensitive to chemical changes and the microenvironment around the functional groups. Thus, it can monitor changes related to tertiary structure as well as secondary structure of proteins. An important advantage of this technique is its versatility in application to samples which may be in solution or solid, clear or turbid, in aqueous or organic solvent. Since the concentration of proteins typically found in food systems is high, the classical dispersive method based on visible laser Raman spectroscopy, as well as the newer technique known as Fourier-transform Raman spectroscopy which utilizes near-infrared excitation, are more suitable to study food proteins (Li-Chan et aL, 1994). In contrast the technique based on ultraviolet excitation, known as resonance Raman spectroscopy, is more commonly used to study dilute protein solutions. 

Representative emission spectra are shown schematically in Fig. 2.2 for hydrogen, potassium, and mercury on a common wavelength scale from the near infrared to the ultraviolet. Under the coarse wavelength resolution of this figure, the emitted light intensities are concentrated at single, well-defined emission lines. In H, the displayed emission consists of four convergent series of lines, the so-called Ritz-Paschen and Pfund series in the near infrared, the Lyman series in the vacuum ultraviolet, and the Balmer series in the visible. Johann Balmer, a schoolteacher in Basel in the late nineteenth century. 

Absorption losses caused by electronic transitions and molecular vibrations are examples of intrinsic mechanisms. For sihca, the electronic transitions are in the ultraviolet (UV) wavelengths, whereas the molecnlar vibrations are in the infiared (IR). The tails of these transitions bracket the usefiil range of low loss between the visible and the near-infrared wavelengths. Impurity absorption losses are examples of extrinsic mechanisms. The main impurities in fibers made by vapor deposition techniques are the transition metal ions and OH ions. Impurities such as iron cause absorption in the UV and visible wavelengths. Their concentrations need to be lednced to the few parts per bilhon range to reduce their contributions to... 

Ruby was the first material for lasers but several other crystals are now employed. The crystals used need to contain an impurity with an energy level such that return to the ground state is only possible by a forbidden transition in the infrared, visible, or near ultraviolet. It must also be possible to populate this level via an allowed (or at least less forbidden) transition. Research has tended to concentrate on transition metal ions and lanthanide ions in various hosts since these ions have suitable transitions of the... 

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