Short wavelength region

It has been found (7,9) that Z) > 0, ie, the maximum of an asymmetrical dye, X, is shifted to the short-wavelength region with respect to the arithmetical mean of the parent dye maxima. The phenomenon has been named a deviation (7). The positive deviations in PMDs are explained by the bond order alternation within the polymethine chain caused by different contributions of both end groups to the dye energetic stabiUty (7,9,10). The deviation reaches its maximum at Tqi > 45° and Tqi < 45° if the end groups have > 45° and 4>q2 > 45°, or < 45° and 4>q2 < 45°, then the... 

The change in the optical absorption of et7 with time (at 77 K) is shown in Fig. 5. It can be seen that electrons stabilized in shallower traps decay more rapidly due to which, in the course of the reaction, the absorption spectra shift steadily to the short-wavelength region, and the rate of the change of the optical density depends on the wavelength. This somewhat hinders the quantitative analysis of the kinetic data obtained for reaction (4) by the optical method. At the same time, the width and the shape of the EPR lines of et7 remain unchanged as kinetic measurements are made. This makes the analysis of the kinetic data much simpler since, in this case, the amplitude of the et7 EPR spectrum can be taken directly as a value characterizing the concentration of etr. For this reason most of the kinetic measurements for reaction (4) have been made by the EPR method. 

Workers at PerkinElmer (Perkin Elmer Ltd., Beaconsfield, UK, Private Communication) claim that sensitivity and precision in lead determinations in spinach were both improved by using the L vov platforms as opposed to normal off the wall techniques. This is because dependence on temperature is reduced. Johns et al. [26] has described a quantitative thin-layer chromatographic procedure for the determination of lead in plant tissues. The method is based on the use of ammonium pyrrolidinedithiocarbamate for the extraction and enrichment of lead. Instead of the previously reported conversion and visualisation of the lead complex in the short wavelength region using dithizone, the lead carbamate was converted to lead sulfide with the aid of a 6% solution of sodium sulfide in methanol/water (3 1) on silica plates, after development of the plates with toluene. See also Sects. 7.34.1,7.34.4 and 7.34.5... 

In the optical case the transition amounts to taking wavelength into account - in the mechanical case Planck s constant becomes a factor, also in the short-wavelength region. There is no implication that the classical equations describe fundamentally different situations. They are simply less detailed than their non-classical analogues and more convenient to use in the macroscopic world. The two sets of equations deal with the same concepts at different levels of refinement. Apart from Planck s constant quantum theory does not introduce any additional concepts, unknown to classical theory, but it has the ability to explain some experimental results that baffled classical science. 

We have already described the radiation spectrum of the sun and noted that the major portion of solar energy is concentrated in the short-wavelength region. It was also noted that as a consequence of this spectrum, real surfaces may exhibit substantially different absorption properties for solar radiation than for long-wavelength earthbound radiation. 

Figure 5a shows CD spectra of tartaric acid, which has an absorption i the short wavelength region and thus is prone to suffer from dispersion effect as compared with transition metal complexes. Two solution spectra in solvent of different polarity, water and dioxane, are similar to each other, but the CD C a nujol mull is quite different from that in solution. A KBr disc prepared t avoid dispersion effects gave a solid-state tartaric acid spectrum similar to thi in solution (Fig. 5b). Thus the difference between the nujol mull CD and solutid CD is not due to the different molecular conformation or intermolecular intera tion in the two phases. Most likely, it is due to the dispersion effect in the cas of the nujol mull form. Many nujol mull CD spectra of organic compound have been reported recently, but most of them appear to suffer from substanth dispersion effects. It is to be noted that the dispersion terms for molecules C...

By phenyl substitution on the pyridine moiety or by using isoquinolinium-N-oxides the absorption of the pyridinium salts can be extended to longer wavelengths [47]. Table 3 summarizes the absorption characteristics of the pyridinium salts which are used as cationic photoinitiators. In Fig. 2 the absorption maxima are compared to the emission lines of mercury. The photosensitivity of these pyridinium salts lies in the short wavelength region of the UV spectrum. Thus, pyridinium salts have to be used with sensitizers or free radical sources in order to extend their sensitivity into the region between 350-400 nm. 

Since Ophotoeiectric cxists only on the short wavelength region of the absorption edge, so also does f"(0). The dispersion of f"(0) is fully controlled by Ophotoeuctric- For the K edge, aph , eiectric represented fairly well by the empirical formula... 

As is evident from this table brown glass containers may not provide sufficient photo protection for all drug substances/products. Brown glass absorbs UV and VIS radiation up to about 450 nm. The short wavelength region up to about 350-400nm is almost quantitatively absorbed, depending on the samples thickness. 

The scintillation counter (Sec. 7-7) and the sealed gas proportional counter (Sec. 7-5) are both used in spectrometry. The scintillation counter is better for the very short wavelength region because of its greater efficiency there (Fig. 7-12) in the 1 A-2 A range either counter is suitable. In the long-wavelength region a gas-flow proportional counter is required, because of its thin low-absorption window. 

The range of application into the short-wavelength region of the spectrum depends on the window material employed in the photomultipher. Borosilicate glass (Kovar glass), for example, only transmits radiation down to about 280 nm. 

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