Infrared transmission

Table 7.29 Infrared Transmission Characteristics of Selected Solvents...

TABLE 7.29 Infrared Transmission Characteristics of Selected Solvents Transmission below 80%, obtained with a 0.10-mm cell path, is shown as shaded area. 

Selenium chalcogenide glasses exhibit good infrared transmission properties. These are used as lenses (ZnSe, CdSe) in laser apphcations and have potential applications in fiber optics (qv) and in data storage and retrieval. 

Figure 11 Mid-infrared transmission spectra recorded from a linear (high-density) polyethylene before, during and after oxidation at 145°C (a) OH stretching region, (b) carbonyl stretching region. Reproduced from Luongo [23]. Copyright 1960 John Wiley Sons, Inc.

Coleman and Sivy also used an infrared transmission cell to undertake degradation studies under reduced pressure on a series of poly(acrylonitrile) (ACN) copolymers [30-33]. Thin films prepared from a polymer were mounted in the specially designed temperature-controlled cell mounted within the infrared spectrometer. The comparative studies were made on ACN copolymers containing vinyl acetate [30,32], methacrylic acid [30,31] and acrylamide [30,33]. The species monitored was the production of the cyclised pyridone structure. This was characterised in part by loss of C=N stretch (vC = N) intensity at 2,240 cm-1 accompanied by the appearance and increase in intensity of a doublet at 1,610/1,580 cm-1. 

Infrared transmission spectra were measured on self supported wafers (2 cm2, 20 mg), in a quartz IR cell allowing sample heating under vacuum and introduction of standardised volumes of gas. The samples were activated under vacuum (106 torr) by heating (1 K.min 1) up to 673 K. 

Another demonstration that hydrogenation neutralizes acceptors is the decrease in free-carrier absorption observed during infrared transmission experiments by Pankove et al. (1985). 

Figure 5. Comparison between infrared transmission (A) and reflection-absorption (B) methods for obtaining spectra of LB films.

Figure 17. Infrared transmission spectra of the alternating S(PS)9-Ba film at various temperatures [7].

J. E. Peters and P. D. Ownby. Far Infrared Transmission of Diamond Structure Semiconductor Single Crystals-Silicon and Germanium , Optical Engineering, Vol. 38, No. 11, pp. 1924-1931, November 1999. 

In symposia such as the present one, and especially in topical meetings concerned with "surface analysis," it is becoming increasingly rare to find work stressing infrared transmission/-absorption spectroscopy (IR-T/A) per se. This is not because... 

H. Martens, J.P. Nielsen and S.B. Engelsen, Light scattering and light absorbance separated by extended multiplicative signal correction. Application to near-infrared transmission analysis of powder mixtures, Anal Chem., 75, 394 (2003). 

Germanium dioxide has high refractive index and infrared transmission, for which it is used in industrial glasses. It also is used in preparation of high purity grade germanium. 

There have been many investigations of photoinduced effects in -Si H films linked to material parameters. Changes have been observed in the carrier diffusion length, unpaired spin density, density of states in the gap, and infrared transmission. The transition from state A to B seems to be induced by any process that creates free carriers, including x-ray radiation and injection (double) from the electrodes. Because degradation in a solar cell is accentuated at the open-circuit voltage conditions, the A to B transition occurs upon recombination of excess free carriers in which the eneigy involved is less than the band gap. It has been pointed out that this transition is a relatively inefficient one and the increase in spin density takes place at a rate of 10-8 spins per absorbed photon. 

Figure 6. Infrared transmission spectra of a photocured epoxyacrylate film (30 ytm) before and after aging in an Atlas UVCON. (Reproduced with permission from Polym. Deg. Stability Ref. 37).

In its applications to spectra on finely divided metals DRIFTS is similar to infrared transmission. Its advantage is that catalysts can be studied in powdered form, even in situ during catalytic reactions, thus avoiding some of the diffusion-limited kinetics that are encountered when pressed catalyst disks are used. 

The STG was cast from alx 10 3 M solution into which the mirror had been immersed for from 10 to 20 min (see Appendix 1). The presence of a monolayer was confirmed by ellipsometry (18 A). The spectral data agreed with data gathered on a similar system in a powder form. In this case, CuzO powder was immersed in a 0.01 M solution of isooctyl thioglycolate (OTG) in isopropanol for from 1 to 10 min, washed with pure isopropanol, dried in air, and analyzed via infrared transmission in a KBr dispersion pellet (see Appendix 2). A similar spectral shift of approximately 15 cm 1 (1739— 1724 cm-1) was observed and the lack of two distinct carbonyl absorbances suggested the formation of a monolayer. In both cases, the formation of a copper-mercaptoester salt may be responsible... 

Each oxide powder was washed copiously with pure isopropanol, dispersed in a KBr pellet, and analyzed via infrared transmission for organic contaminants and to obtain reference spectra of the blank oxides. The washed powders were then air-dried and placed aside in a desiccator. Next, 500 ml of 0.01 M solution of isooctyl thioglycolate (OTG) in isopropanol was prepared and 15 ml glass vials were then filled with approximately 0.50 g of each powder. This was followed by the addition of about 10 ml of the OTG solution to each vial. The vials were then seated and agitated for about 10 min. This... 

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