Visible spectrochemical analysis

If appropriate corrections are made for scattering and related effects, tile ratio I/Io is given by the laws of Bouguer and Beer. Here, I0 is the intensity or radiant power of the light incident on the sample and / is tile intensity of the transmitted light. This ratio ///o = T is known as the transmittance. See also Spectrochemical Analysis (Visible). 

PHOTOMETRIC ANALYSIS. Chemical analysis by means of absorption or emission of radiation, primarily in the near UV, visible, and infrared portions of the electromagnetic spectrum. It includes such techniques as spectrophotometry, spectrochemical analysis, Raman spectroscopy, colorimetry, and fluorescence measurements. 

SPECTROCHEMICAL ANALYSIS (Visible). Chemical systems that exhibit a selective light absorptive capacity are colored. Hence, the terms colorimetric analysis and colorimetry often are used to designate the measurement of such systems when the objective is to determine the concentration of die constituent responsible for the color. The use of the term colorimetry in this respect is not to be confused with the use of the same term in physics where the term refers strictly to the measurement of color. See also Colorimetry. 

X-ray spectroscopy rivals visible spectroscopy as a tool for elemental analysis. Because the energies of x-rays are much higher than those of visible radiation, however, x-rays usually cause transitions of inner-shell electrons rather than of valence-shell electrons. There are many advantages of this method in spectrochemical analysis. A quantitative analysis of a mixture of rare-earth oxides may be performed or a crystal structure may be determined. A specimen that contains two elements widely separated in atomic number may be studied, or the thickness of a very thin layer of tin plating may be measured. The most widespread use of x-rays has been in the field of metallurgy, but x-rays may also be used to analyze metals, minerals, liquids, glasses, ceramics, or plastics. 

Ion Beam Spectrochemical Analysis. As remarked earlier, ion irradiation of a surface produces visible light photons as well as many other types of particle. The light emission arises from the deexcitation of ions and excited neutrals, and is characterized by a spectrum consisting of a series of sharp lines at wavelengths associated with the type of ionized or excited atom. Spectral analysis thus provides elemental identification by reference to standard emission wavelength tables. 

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