Absorption, measurement scanning curves

ABP = 2-amino-5-bromophenyl(pyridin-2-yl)methanone 226,227 Absorbance, determination of 31 Absorption, measurement of 9,17,31 molar coefficient 36, 40 quantitative relationship 35, 36 recording of spectra 30, 31 -bathochromic/hypsochromic shift 31 -comparison to spectra of solutions 31 scanning curves 17,31,32 ACB = 2-amino-5-chlorobenzophenone 227... 

Fig. 9.5 Simultaneously measured CV curve (a), absorption potential curve (b), and its derivative with respect to scan potential (c), for the cyclic linear sweep oxidation of tri-p-anisylamine at a vapor-deposited platinum OTE in 0.1 M Et4NCI04-AN [8].

The shape of the Z-scan curve can be modified if a nonlinear absorption or nonlinear transmission (absorption bleaching) takes place in the sample, e.g., due to the presence of an imaginary part of 3) of the material. The curves then become asymmetrical due to increased absorption or transmission when the sample is close to the focal plane. By analyzing the shape of such a modified Z-scan curve, one can determine the nonlinear absorption coefficient f32 or the related imaginary part of 3). Alternatively, to determine the nonlinear absorption properties of a sample, the total transmission through the sample can be monitored, i.e., the total intensity of the transmitted beam can be measured without an aperture, as a function of the sample position with respect to the focal plane. Such an experiment is usually referred to as an open aperture Z-scan. It is often used for the investiga-... 

Silicon films that were electron beam evaporated at a rate of 5 nm sec-1 on silica substrates at 440°C were subsequently irradiated with an Ar+ laser. The rapidly scanned Gaussian beam formed a smooth lateral temperature gradient in the film hence it provided a simple means to study the crystallization mechanism. The laser-heated track reveals two easily discernible areas. A 1 -//m-thick film showed color changes from black to deep red at the margins of the track to light yellow in the middle of the track. Despite the smooth fall of the laser intensity, the different boundaries are abrupt. Optical absorption measurements of the respective areas are also displayed in Fig. 1. The curve E440 represents the as grown evaporated film and is in... 

Figure 3.45. (a) Current-voltage curve of (100) Ge electrode in 1 /W HCIO4 electroiyte taken when spectra shown in Fig. 3.44 were measured. Scan rate 10 mV s . p) Free-eiectron and free-hole absorption during potential scan under same conditions as in Fig. 3.43. Adapted, by permission, from F. Maroun, F. Ozanam, and J.-N. Chazaiviei, Surf. Sc/. 427-428,184 (1999), p. 185, Fig. 1 and p. 188, Fig. 3. Copyright 1999 Elsevier Science B.V.

One problem with methods that produce polycrystalline or nanocrystalline material is that it is not feasible to characterize electrically dopants in such materials by the traditional four-point-probe contacts needed for Hall measurements. Other characterization methods such as optical absorption, photoluminescence (PL), Raman, X-ray and electron diffraction, X-ray rocking-curve widths to assess crystalline quality, secondary ion mass spectrometry (SIMS), scanning or transmission electron microscopy (SEM and TEM), cathodolumi-nescence (CL), and wet-chemical etching provide valuable information, but do not directly yield carrier concentrations. 

Figure 7.34. ATR unpolarized difference spectra of galena-0.01 M borate, pH 9.18, interface during positive scan. Smooth background at low frequencies (dashed lines) arises from free-hole absorption. Reference for spectrum marked by -0.40 V is spectrum measured at -0.50 V after reduction. Each of the other curves is spectrum measured at indicated potential after subtracting spectrum measured at preceding potential. Horizontal lines indicate zero absorbance. Reprinted, by permission, from I. V. Chernyshova, J. Rhys. Chem. B 105, 8178 (2001), p. 8180, Fig. 2. Copyright 2001 American Chemical Society.

The spot can be measured as a whole or in segments when a suitably shaped light beam is used. Usually the spot area is scanned with a narrow beam and the diminution in light intensity summed for the spot area. One might expect that, under the conditions mentioned on p. 136, a linear relation would be found between the areas under the extinction curves thus obtained and the amounts of substance applied. As Klaus [351] has shown, the absorption integrals are, however, independent of the spot shape only when the transmission is relatively high, the spot area not too small and the spot fairly symmetrical. Standard and sample must be chromatographed on the same layer in order to compensate for individual infiuences of the adsorption layer. 

The characterization methods applied to light-powered actuators encompasses a large array of techniques, most of which are common to viscoelastic materials, such as stress-strain curves, differential scanning calorimetry (DSC), and so on. For annealed films, the thickness with respect to the input information (light source) is measured by ellipsometry or neutron reflectivity, both of which are sensitive analytical tools for film thickness. The major analytical technique that differs from those already discussed in this chapter is UV-vis spectroscopy as it can be used to monitor the extent of photoisomerization. The different isomers give rise to different spectral absorption bands, which can be followed during the photo-illumination process. 

The determination of the uranyl ion concentration by means of an absorbance measurement involved two basic steps. First the wavelengths from 400 to 600 nm were scanned using 4 x IO" molar aqueous uranyl ion solution. An absorption maximum at 415 nm was obtained. Second, a calibration curve (Absorption vs Concentration) was made over the concentration ramge from 0.1 to 4 X 10" molar at 415 nm. Concentrations were determined by means of this calibration curve. An aqueous solution of PANa (4 X 10" molar) was scanned from 400 to 600 nm. No absorbance was noted. Aqueous solutions of UNHH were observed for 30 days employing the wavelength of 415 nm. No change was noted. Reaction mixtures containing UNHH and PANa were scanned from 400 to 6OO nm after removal of the precipitated material. 

Tg measurement by differential scanning calorimetry (DSC) defines the Tg as a change in the heat capacity of the material. The deflection in the heat rate absorption curve, W/g/°C, is used to identify the second-order thermodynamic change from a glassy sohd to an amorphous solid that is the glass transition. 

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