Spectrum transmittance

Fig. 21.12 Optical transmittance spectra of the BaBPOs crystal (a) pristine crystal (b) after irradiation by X-rays for 15 min (c) after annealing at 150°C for 1 hour of the X-ray-irradiated sample.

We keep learning more about the history of noise calculations. It seems that the topic of the noise of a spectrum in the constant-detector-noise case was addressed more than 50 years ago [1], Not only that, but it was done while taking into account the noise of the reference readings. The calculation of the optimum absorbance value was performed using several different criteria for optimum . One of these criteria, which Cole called the Probable Error Method, gives the same results that we obtained for the optimum transmittance value of 32.99%T [2], Cole s approach, however, had several limitations. The main one, from our point of view, is the fact that he directed his equations to represent the absorbance noise as soon as possible in his derivation. Thus his derivation, as well as virtually all the ones since then, bypassed consideration of the behavior of noise of transmittance spectra. This, coupled with the fact that the only place we have found that presented an expression for transmittance noise had a typographical error as we reported in our previous column [3], means that as far as we know, the correct expression for the behavior of transmittance noise has still never been previously reported in the literature. On the other hand, we do have to draw back a bit and admit that the correct expression for the optimum transmittance has been reported. 

Fig. 2.5. p- and j-polarized vs transmittance spectra of the monolayer l2Cl[Pg.9]

Fig. 2.6. p- and -polarized vt transmittance spectra of the monolayer 12C1602/NaCl(100) at T- 80 K (C02 pressure lxlO 9 mbar, instrumental resolution 0.05 cm-1).40... 

Fig. 2.8. Monolayer transmittance spectra of the adsorbate 12C160/NaCl(100) for different temperatures. Angle of incidence 50 1°.27,28...

Infrared microscopy combines an optical microscope with an FT-IR spectrometer enabling pico- to femtogram (10 12—10 15 g) quantities of substances to be characterized or very small areas of larger samples to be analysed. Beam-condensing optics focus the radiation onto an area of the sample identified using the optical microscope and either reflectance or transmittance spectra can be recorded. The highly-sensitive MCT detector (p. 283) is normally used as its size can be matched to that of the radiation beam to maximize its response. 

Fig. 4. Transmittance spectra of filters with a bandpass for UV (A), visible (B), and red to near-infrared (C).

FTIR spectrometers generally provide transmittance spectra, T (v). Three steps are realized before the final spectrum of a sample is obtained ... 

Two samples of the same phosphor crystal have quite different thicknesses, so that one of them has a peak optical density of 3 at a frequency of vo. while the other one has a peak optical density of 0.2 at vq. Assume a half width at half maximum of Av = IGHz and a peak wavelength of 600 nm, and draw the absorption spectra (optical density versus frequency) for both samples. Then show the absorbance and transmittance spectra that you expect to obtain for both samples and compare them with the corresponding absorption spectra. (To be more precise, you can suppose that both bands have a Lorentzian profile, and use expression (1.8), or a Gaussian line shape, and then use expression (1.9).)... 

Transmittance and reflectance data are used in color measurements. Transmittance spectra are used for liquid color measurements, while reflectance spectra are used on solid samples (powders, surfaces) and on opaque liquids (paint). A large number of color scales are in use today. Some are specific to a particular industry, while others enjoy broader application. The most common scales are the CIE L a b (Commission... 

S.R. Delwiche, K.H. Norris and R.E. Pitt, Temperature sensitivity of near-infrared scattering transmittance spectra of water-adsorbed starch and cellulose, App/. Spectrosc., 46, 782-789 (1992). 

Fig. 5.33 Transmittance spectra of glass (Corning 2947) substrate, and 450°C aimealed nanotubular titania film atop same glass (Corning 2947) substrate.

Present data illustrate the technique for an in situ determination of surface areas. Related methods had been applied primarily to the study of site distributions in clay minerals, particularly by Russian workers (66), and they were used by Bergmann and O Konski in a detailed investigation of the methylene blue-montmorillonite system (3). In fact, changes in electronic spectra arising from surface interactions received sufficient attention in the past to warrant their review by A. Terenin (65). Most of these investigations involved transmittance spectra but new techniques in reflection spectrophotometry and applications of the Kubelka-Munk relation have facilitated the quantitative evaluation of spectra in highly turbid media (35, 69, 77). Thus, in agreement with the work of Kortiim on powders and anhydrous dispersions (31, 32, 33), our results demonstrate the applicability of the Kubelka-Munk function... 

Iodine number as well as melting point is one of the most important factors for quality control of processed fats and oils. However, a time-consuming chemical analysis is generally used for determining iodine number which sometimes stops production. In order to overcome this problem, an on-line NIR sensor has been developed [10]. Transmittance spectra of many kinds of oils were measured in the wavelength region from 1100 nm to 2500 nm to make a calibration equation. 

FIGURE 2.27 UV transmittance spectra of PC, PMMA, glass, and PDMS substrates [224]. Reprinted with permission from the American Chemical Society. 

Fig. 14 Far-infrared transmittance spectra for rhombohedral (R) and orthorhombic (O) C60 polymers, and for C60 dimers, measured near 20 K. Curves are offset for clarity. Reprinted with permission from VC Long, JL Musfeldt, K Kamaras, GB Adams, JB Page, Y Iwasa, and WE Mayo, CFar-infrared vibrational properties of high-pressure high-temperature C60 polymers and the C60 dimer , Phys. Rev. B vol. 61 (2000) 13191-201 [100]. Copyright 2000 The American Physical Society...

Fig. 2. Monolayer transmittance spectra of the adsorbate 12CO on NaCl (100) at various temperatures (angle of incidence 50 1°) [adapted from Heidberg et al. (48) with permission of Elsevier Science Publishers],...

LP-CVD ZnO Optical total and diffuse transmittance spectra (TT and DT spectra) of a temperature series of undoped LP-CVD ZnO films are shown in Fig. 6.25 TT does not vary strongly with substrate temperature. Indeed, as Fig. 6.25 is related to a series of undoped samples, the values of carrier density N are too low to produce an observable free carrier absorption effect... 

Total and diffuse transmittance spectra (TT and DT, resp.) and haze factor (i.e., DT/TT measured at 600 nm) are presented in Fig. 6.29 as a function of the H2O/DEZ ratio. As the thickness d of the ZnO samples does not vary significantly within this series, we may assume that the trends observed hereafter are not due to a variation of d. TT does not vary within this series, with the single exception of the TT curve for the ZnO sample deposited with a H2O/DEZ ratio of 0.8, i.e., the only sample deposited with an excess of DEZ. The TT of this sample is systematically lower than the TT curves of the ZnO samples deposited with an excess of water. The reduction of TT in the NIR area is similar for all the curves. This indicates that free carrier... 

Reflectance data can be more deceiving with respect to the quantitative composition than transmittance data, as illustrated in Figure 6. Equivalent reflectance and transmittance spectra (Figure 6A) are converted into absorbance Ae and F(p) (Figure 6B and C). The F(p) representation... 

Figure 13.4 Optical transmittance spectra for Au nanoparticles formed by annealing Au-implanted MgO in H2 (solid line) and 02 (dashed line) atmospheres.

Figure 1. Transmittance spectra of films prepared in 10.4% oxygen partial pressure at different annealing temperature in air.

Figure 5.1-3a/b Definition of Iq and / for the determination of absorbance values from transmittance spectra. 

Figure 5.1-9 Infrared transmittance spectra for the determination of impurities of oxygen and carbon in Si wafers (sample thickness 0.5 mm, resolution 4 cm ).

Quite early in the history of infrared spectroscopy, reflections in form of reststrahlen bands were observed indicating strong absorption. Nowadays infrared spectroscopy is widely applied to organic compounds which are comparably weak absorbers. For their studies such reflection methods are favoured, whose results are interpretable in almost the same way as transmittance spectra are. However, there is an increasing interest in applying other reflection techniques also to such samples. Advantageous aspects are ... 

For the strong oscillator the n and k spectra are asymmetric. The shift of the k maximum away from the resonance frequency is particularly obvious. In such a case a reliable representation of the vibrational structure cannot be derived from transmittance spectra and thus, from the absorption index k alone. Another peculiarity of the strong oscillator is the spectral range where the (real) refractive index is below unity. This renders... 

Generally, the assumption is made that scattering does not depend on the wavenumber so that the conversion of the measured reflectance spectrum R by means of the Kubelka-Munk function F R), results in an absorption-proportional representation. As for ATR and reflection-absorption spectroscopy, also the diffuse-reflectance spectmm does not consist of dispersion features but band-like structures. For changes in low absorption, the sensitivity of diffuse reflectance is greater than the one of transmittance, while strong absorption bands are less pronounced in the diffuse-reflection (see Fig. 6.4-18). Therefore, diffuse-reflection spectra resemble poorly resolved transmittance spectra. For diffuse reflectance spectra where R is in the order of 0.01 or below, the function -log R or just I / R is equally well suited for conversion (Olinger and Griffiths, 1988). Such level are found with compact samples such as polymer foams or varnishes with filler (Otto, 1987 Korte and Otto, 1988). 

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