Spectral absorptance

The intensity of a spectral absorption band at a given wave length is expressed in terms of absorption or extinction coefficients, dehned on the basis of the Beer-Lambert law. The latter states that the fraction of incident light absorbed is proportional to the number of molecules in the light path, i.e., to the concentration (c) and the path length (1). The law may be expressed mathematically as ... 

Gr. prasios, green, and didymos, twin) In 1841 Mosander extracted the rare earth didymia from lanthana in 1879, Lecoq de Boisbaudran isolated a new earth, samaria, from didymia obtained from the mineral samarskite. Six years later, in 1885, von Welsbach separated didymia into two others, praseodymia and neodymia, which gave salts of different colors. As with other rare earths, compounds of these elements in solution have distinctive sharp spectral absorption bands or lines, some of which are only a few Angstroms wide. 

Sensitizers as well as desensitizers form a reversal oxidoreduction system with silver halides, according to both pH and pAg of the photographic emulsion. But besides the specific influence of the emulsion, the efficiency of a sensitizing dye depends on many other factors such as its adsorption, its spectral absorption, the energetic transfer yield, the dye aggregate to the silver halide, and finally on its desensitizing property in... 

The amount of a particular component in a sample can be monitored by examining the height of a spectral absorption peak The reduction of an aldehyde to an alcohol would show up as a decrease in line intensity for the carbonyl and an increase for the hydroxyl peaks in the spectrum. Changes in the relative importance of different relaxation modes in a polymer can also be followed by the corresponding changes in a mechanical spectrum. 

Table 10. Spectral Absorption Data for Aqueous Plutonium Ions at 25°C ...

Dye Developers. In addition to having suitable diffusion properties, dye developers must be stable and inert in the negative before processing. After completion of the process, the dye developer deposited in the image-receiving layer must have suitable spectral absorption characteristics and stabiUty to light. 

As previously mentioned, hydrogen bonding changes spectral absorption positions. 

In colorants, the spectral absorption pattern and the extinction coefficient are determined by the chromophore and rarely by side groups of the molecule, p-carotene and zeaxanthin contain the same chromophore but their molecular masses... 

To finally detect the fight after its interaction with the sample to be evaluated for its spectral absorptivity or reflectivity, optoelectric devices are employed. They transform fight signals into electric signals. Two different main types are in use. 

The spectral absorptions shift to longer wavelengths as the solvent polarity increases. However, care must be taken to distinguish them from the spectral shifts due to deprotonation. 

Jelley EE. 1936. Spectral absorption and fluorescence of dyes in the molecular state. Nature 138 1009-1010. 

In order to investigate this effect, ordered arrays of metallic nano-islands were fabricated on glass substrates by a process of natural lithography using monodisperse polystyrene nanospheres. The metal particle dimensions were tailored in order to tune the plasmon resonance wavelength to match the spectral absorption of the fluorophore. The fluorophore, Cy5 dye, which is widely used in optical immunoassays and has a medium quantum efficiency ( 0.3), was used in this preliminary study of the plasmonic enhancement effect. 

The use of infrared (IR) as a technique for structure determination is not very common in recent times. The reviews by Kurzer <1965AHC(5)119, 1982AHC285> contain a table of IR spectral absorptions of 1,2,4-thiadiazoles which covers spectra published before 1982. Additional spectral data was published in CHEC(1984) <1984CHEC(6)463>. 

Fig. 13.11 (a) The molecular absorbance MNF sensor (inset PTCDA molecule) (b) Evolution of spectrum of submonolayer deposition at 1,2, 4, and 8 s after beginning of molecule exposure (c) Subsequent evolution of the spectral absorption at constant molecule number at 13, 53, 413, and 2,393 s after beginning of molecule exposure. Reprinted from Ref. 19 with permis sion. 2008 Optical Society of America... 

Anthraquinone dyes are second only to azo dyes in importance as disperse dyes and are predominant in the red, violet, blue and blue-green sectors [14]. Because anthraquinone disperse dyes are relatively expensive to manufacture, successful attempts were made to replace some of them with technically equivalent and more economical products [15]. The replacement process has been most successful in the red region using, for example, heterocyclic azo dyes and novel chromogens. The brilliance of the anthraquinones with their narrow spectral absorption bands is difficult to attain with other structures, however, as is their high light fastness and chemical stability. The development of anthraquinone disperse dyes is included in a review by Dawson [16]. 

The tinctorial strength in white reductions is thus quantitatively defined by the Kubelka-Munk relation between the spectral absorption coefficient K and the spectral scattering coefficient S in which [ refers to the reflection of a completely opaque layer. The ratio K/S is proportional to the tinctorial strength. 

The value of the incident radiant energy Po may be achieved by drawing a straight line tangent to the spectral absorption curve at the position of the analyte s absorption band. Consequently the transmittance P is usually measured at the point of maximum absorption. Finally, the value of log Po/P is plotted against the concentration as shown in Figure 22.5. 

This chapter shows that zeolite L is a very suitable host for the arrangement of a wide variety of chromophores. The structure of zeolite L is such that the formation of non-fluorescent dimers inside the channels can be prohibited and chromophores can be aligned in a certain direction. We have shown that this host-guest system can be used to make very efficient nanoscale two-directional photonic antenna systems. A broad spectral absorption range can be achieved by using several different cationic and neutral dyes. 

These regions are particularly useful since few, if any, reactions of transition metal complexes are unaccompanied by spectral absorption changes in these regions. We first show how optical absorbances may be substitued for the concentration changes required in deriving the rate law. 

However, the ionic coupling-complexation model is more appropriate to the actual complexity of aqueous solutions, as is evident from spectral absorption and ionic conductivity studies. 

Table 1 can be used as a guide to define hazardous wastes from textile plants. Besides the direct toxicity of substances like chlorinated hydrocarbons, organo-Hg compounds, or concentrated alkaline solutions, other parameters have been defined with regard to problems during biodegradation or accumulation in the sludge from CWWT. A particular situation is found with colored effluents, where limits for spectral absorption have been defined. While the toxicity of textile dyes is comparably low, these limits were derived from the visual aspect of the water released from a textile plant because they look unhealthy. ... 

---