Infrared transmittance spectra

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...

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 ).

Figure 3. Infrared transmittance spectra of Nafion 142 in the acid form at low water content (A), intermediate (B), and high water content (C). Spectra A and B have been moved up the transmittance...

Figure 4. Optical image and two infrared images of a dividing cell (35 pm x 20 pm) obtained from IR spectromicroscopy. These chemical maps are derived from the strength of absorption bands from approximately 100 infrared transmittance spectra collected over the area of the dividing cell. The maximum in the color scale (yellow) represents the position of the maximum absorption by the cell, while the minimum (blue) represents no absorption by the cell. Strikingly, the intensity map of the amide II absorption band shows two peaks in the center of the two halves of the cell, representing the position of two separate nuclei before the cell division is complete. The intensity map of the C-H stretch absorption bands shows that lipids are concentrated at the contractil ring, where the cleavage furrow is located. [Used by permission of the National Academy of Sciences, U.S.A., from Jamin et al. (1998), Proc Natl Acad Sci, Vol. 95, Fig. 3, p. 4839.]...

The chemical structure of the films and particularly the incorporation of hydrogen were studies by FTIR (Perkin Elmer 1760). Fig. 8 shows infrared transmittance spectra of silicon carbonitride films (a) and silicon nitride films (b) deposited at 1123 K. The clusters of absorption peaks that appear in both spectra in the 1300 to 1940 and 3320 to 3900 wavenumber (cm i) regions are attributed to atmospheric moisture. CO2 is also detected at around 2345 cm i. For spectrum (b), the strong band at 847 cm-i indicates the formation of amorphous silicon nitride [161. The much weaker peak at 3326 cm i which is due to a N—H stretching vibration indicates the existence of N—H bonds in the films. The Si—N band at 847 cm i appeared to be broadened near its base line around 1173 cm i. This is due to the existence of N-H bonds which exhibit another bending mode at 1170 cm l All the films displayed similar spectra, and there was no indication of an Si—H bond in silicon nitride. In addition to the stro line at 837 cm, resulting from the fundamental stretching of silicon carbonitride [17], the main difference between spectra (a) arid (b) is the presence of a weak Si—H band, which is observed to be more intense in the films deposited below 1123 K. None of the films exUbited the C—H band around 2900 cm i, which is present in the IR spectrum of the precursor. 

Fig. 21. Infrared transmittance spectra for a YH film corresponding to the (a) as-deposited, (b) dihydride and (c)...

In this context, efforts were made to demonstrate the formation of pores and their effect on specific gravity, specific surface area and cation exchange capacity of three types of residues (produced by using NaOH aqueous solution and its spent solution (the filtrate), respectively). Based on N2 gas absorption, isotherms and infrared transmittance spectra, residues obtained from second and third steps (each of 24 h) of the treatment by filtrates of 1.5 M NaOH were established to be significantly enriched in finer meso- and micro-pores, respectively, as compared to a pure and macro-porous zeolite 4A (zeolite RZP). 

Figure 2.37 Infrared transmittance spectrum of a c. Spin-thick layer of water.

Figure 1. Infrared transmittance spectrum of Nafion 142 in the sodium form at low water content (about 0.15 H20 per — SOs ) and higher water content (about 4.0 H20 per —SOs ). The upper spectrum has been moved up the transmittance scale by 40%.

Figure 3.105 Infrared transmittance spectrum of PFA film (1.350 mm thickness).

Figure 3.107 Infrared transmittance spectrum of FEP film (1.344 mm thickness). ...

Figure 5.27. The infrared transmittance spectrum (neat) of ethanoic anhydride (acetic any-dride) as a thin film between two sodium chloride (NaCl) windows. 

Figure 5.31. The infrared (transmittance) spectrum of propyl propanoate, CH3CH2CO2CH2 CH2CH3, neat, as a thin film.

Fig. 1. (a) Typical mid infrared transmittance spectrum of zeolite NaA. (b) Spectrum of CO2 adsorbed on zeolite NaA obtained from the COi-loaded sample ratioed against the zeolite background. 

FIGURE 2.7 Infrared transmittance spectrum of Na+ perfluorosulfonic ionomer. 

If the sample is placed in the path of the infrared beam, usually between the source and the monochromator, it will absorb a part of the photon energy having the same frequency as the vibrations of the sample molecule s atoms. The comparison of the source s emission spectrum with that obtained by transmission through the sample is the sample s transmittance spectrum. 

Figure 12.12 An infrared absorption spectrum of ethyl alcohol. CH3CH2OH. Atransmit-tance of 100% means that all the energy is passing through the sample, whereas a lower transmittance means that some energy is being absorbed. Thus, each downward spike corresponds to an energy absorption.

The infrared-absorption spectrum of a substance is ideally a plot of the transmittance or the absorbance of a suitable thickness against the wavelength or wavenumber of the infrared radiation. In practice the losses of intensity by reflection at the surfaces of a sample can often be neglected and then, from equations (2.5) and (2.6)... 

Another important characteristic of bacterial cellulose is its capacity to block most of the ultraviolet radiation from sunlight. The UV spectral region is subdivided into UV-A (320-400 nm), UV-B (280-320 nm) and UV-C (below 280nm). UV-C is not considered here, since it is absorbed by the atmosphere. Figure 17.10 shows the transmittance spectrum of a bacterial cellulose membrane from the UV (250-400 nm) to the near-infrared... 

Figure 2.8 Transmittance spectrum of lactic acid. From Stuart, B., Biological Applications of Infrared Spectroscopy, ACOL Series, Wiley, Chichester, UK, 1997. University of Greenwich, and reproduced by permission of the University of Greenwich.

If the reflectance of a sample is low, as it is with gaseous samples, e(v), is approximately equal to 1 — r(. Thus, for any sample for which a transmittance spectrum with discrete absorption bands can be measured, the emittance spectmm should yield equivalent information. As a result, qualitative analysis of the components of hot gases by infrared emission spectroscopy can be as easy as it is by transmission spectrometry. The problem of obtaining quantitative information by infrared emission spectroscopy is more difficult, since not only must the temperature of the sample be known if the radiant power from the blackbody is to be calculated, but the instrument response function must also be taken into account [1]. 

Figure 3.2 Transmittance spectrum and absorbance spectrum (a) spectrum of infrared radiation emitted from a source B (v) (b) spectrum of infrared radiation emitted from the source after passing through a sample (c) transmittance spectrum T(v) and (d) absorbance...

A spectrum is a graphical representation of how the sample and the light are interacting. Here is an Infrared Absorption spectrum. It shows wavenumbers, which are 1/wavelength v. Transmittance, which is related to absorbance. Chemists learn information about the structure of a compound by interpreting the spectra because each compound has a unique spectra, sort of like a finger print. 

Define Iq to be the intensity of the light incident upon the sample and I to be the intensity of the beam after it has interacted with the sample. The goal of the basic inftared experiment is to determine the intensity ratio I/Iq as a function of the frequency of the light (w). A plot of this ratio versus the frequency is the infrared spectrum. The inftared spectrum is commonly plotted in one of three formats as transmittance, reflectance, or absorbance. If one is measuring the fraction of light transmitted through the sample, this ratio is defined as... 

An example of an absorption spectrum—that of ethanol exposed to infrared radiation—is shown in Figure 12.12. The horizontal axis records the wavelength, and the vertical axis records the intensity of the various energy absorptions in percent transmittance. The baseline corresponding to 0% absorption (or 100% transmittance) runs along the top of the chart, so a downward spike means that energy absorption has occurred at that wavelength. 

All infrared spectrophotometers are provided with chart recorders which will present the complete infrared spectrum on a single continuous sheet, usually with wavelength and wavenumber scales shown for the abscissa and with absorbance and percentage transmittance as the ordinates. More advanced instruments also possess visual display units on which the spectra can be displayed as they are recorded and on which they can be compared with earlier spectra previously obtained or with spectra drawn from an extensive library held in a computer memory. These modern developments have all led to quantitative infrared spectrophotometry being a much more viable and useful analytical procedure than it was just a few years ago. 

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