IR absorption spectra

Figure Bl.22.4. Differential IR absorption spectra from a metal-oxide silicon field-effect transistor (MOSFET) as a fiinction of gate voltage (or inversion layer density, n, which is the parameter reported in the figure). Clear peaks are seen in these spectra for the 0-1, 0-2 and 0-3 inter-electric-field subband transitions that develop for charge carriers when confined to a narrow (<100 A) region near the oxide-semiconductor interface. The inset shows a schematic representation of the attenuated total reflection (ATR) arrangement used in these experiments. These data provide an example of the use of ATR IR spectroscopy for the probing of electronic states in semiconductor surfaces [44]-...

The PLM can be used in a reflection or a transmission mode. With either mode, light of various wavelengths from ultraviolet to infrared, polarized or unpolarized, is used to yield a wide variety of physical measurements. With just ordinary white light, a particle or any object detail down to about 0.5 p.m (500 nm) in diameter can be observed to detect shape, size, color, refractive index, melting point, and solubiUty in a group of solvents, all nondestmetively. Somewhat larger particles yield UV, visible, or IR absorption spectra. 

Fig. 16. IR absorption spectra of the products obtainedfrom a LiF - Ta2Os - NH4HF2 mixture (molar ratio 2 1 10) at 230 V (1), 290% (2), 350 V (3) and 435V (4). Reproduced from [113], V. T. Kalinnikov, Y. I. Balabanov, L. A. Agulyansky, A. I. Agulyansky, Y. A. Serebryakov, Zh. Obschei. Khim. 54 (1984) 1929, Copyright 1984, with permission of Nauka (Russian Academy of Sciences) publishing.

IR absorption spectra of several fluorotantalates of alkali and alkali earth metals prepared by hydrofluoride synthesis are presented in Fig. 17. 

IR absorption spectra of some oxyfluoroniobates prepared by the hydrofluoride method are displayed in Fig. 22. 

According to different authors [28, 77, 78, 115], all compounds mentioned in Table 17 have isolated complexes TaFg3 or NbFg3 in their crystal structure. This is confirmed by similar IR absorption spectra indicating a strong band at -500 cm 1 for all such compounds [115, 119, 137, 138]. 

IR absorption spectra of oxypentafluoroniobates are discussed in several publications [115, 157, 167, 185, 186], but only Surandra et al. [187] performed a complete assignment of the spectra. Force constants were defined in the modified Urey-Bradley field using Wilson s FG matrix method. Based on data by Gorbunova et al. [188], the point group of the NbOF52 ion was defined as C4V. Fifteen normal modes are identified for this group, as follows ... 

At(I, R) + 2Bi(R) + B2(R) + 4E(I, R), where I indicates activity in IR absorption spectra and R indicates activity in Raman spectra. Kharitonov and Buslaev [186] determined the force constant of the Nb=0 bond as being 7.0 mD/A for K2Nb0F5H20. This datum seems to be very close to the data mentioned in Table 25, in which assignment of calculated and observed vibration modes is presented for Rb2NbOF5 and Cs2TaOF5. 

Table 28 presents structural characteristics of compounds with X Me ratios between 6 and 5 (5.67, 5.5, 5.33, 5.25). According to data provided by Kaidalova et al. [197], MsNbsC Fu type compounds contain one molecule of water to form M5Nb303Fi4-H20, where M = K, Rb, Cs, NH4. Cell parameters for both anhydrous compounds [115] and crystal-hydrates [197] were, nevertheless, found to be identical. Table 28 includes only anhydrous compound compositions because IR absorption spectra of the above compounds display no bands that refer to vibrations of the water molecule... 

Table 29 presents IR absorption spectra of the above compounds. All spectra display bimodal absorption in the high frequency range, which is attributed to Nb-0 vibrations. In addition, the Nb-F part of the spectra seems to be different from the typical spectra observed for isolated complex ions. Such differences in the structure of the spectra can be related to vibrations of both the bridge and the terminal ligands. 

Sharing of an oxygen atom by two central atoms in compounds with chain-type structures weakens the binary Nb=0 bond compared to the corresponding bond in pure isolated ions such as NbOF52 This phenomenon affects the vibration spectra and increases wave numbers of NbO vibrations in the case of isolated oxyfluoride complex ions. Table 31 displays IR absorption spectra of some chain- type compounds. Raman spectra are discussed in [212],... 

Table 31. Wave numbers (cm1) of IR absorption spectra of chain-type compounds (Me = Nb or Ta).

IR absorption spectra of Rb2Ta203F6 and Cs7TagOi3F2i are practically identical and are characterized by intensive bands as follows (in cm 1) [115] ... 

In all cases, broad diffuse reflections are observed in the high interface distance range of X-ray powder diffraction patterns. The presence of such diffuse reflection is related to a high-order distortion in the crystal structure. The intensity of the diffuse reflections drops, the closer the valencies of the cations contained in the compound are. Such compounds characterizing by similar type of crystal structure also have approximately the same type of IR absorption spectra [261]. Compounds with rock-salt-type structures with disordered ion distributions display a practically continuous absorption in the range of 900-400 cm 1 (see Fig. 44, curves 1 - 4). However, the transition into a tetragonal phase or cubic modification, characterized by the entry of the ions into certain positions in the compound, generates discrete bands in the IR absorption spectra (see Fig. 44, curves 5 - 8). 

Fig. 44. IR absorption spectra of Li3Ta04 (1), Li4Ta04F (2), LiJJbOfr (3), Li3Ti03F (4)- rock-salt-type structures with disordered ionic arrangement and high-temperature modifications of Li3Ta04 (5), Li4Ta04F (6), Li3Nb04 (7), LiMO.F (8).

Vibration spectra of fluoride and oxyfuoride compounds correspond to X Me ratios, especially in the case of island-type structure compounds. Analysis of IR absorption spectra provides additional indication of the coordination number of the central atom. Fig. 45 shows the dependence on the X Me ratio of the most intensive IR bands, which correspond to asymmetric Me-F modes in fluoride complexes, as well as v(Me=0) and v(Me-F) in oxyfluoride complexes. Wave numbers of TaF5, NbF5 and NbOF3 IR spectra were taken from [283-286]. 

Tsikaeva et al. [290,291] investigated the Raman and IR absorption spectra of hydrofluoric acid solutions containing a wide range of concentrations of niobium, but no other additional cations. 

Fig. 85. IR absorption spectra of gaseous OF collected from the retort atmosphere.

Fig. 86. IR absorption spectra of K NbF7 (curves 1-3) and K7TaF7 (curves 4 - 6) Curve numbers correspond to temperatures in X) ...

The spectrum of the niobium-containing extract was concluded to be related to the presence of NbFg and NbF5OR" ions [462]. Investigation of the IR absorption spectra confirms the presence of TaFe and NbF6 complex ions in the tantalum and niobium extracts, respectively. 

Figure 15-7. (a) Pholoinduccd IR absorption spectra of P30T and P30T/Q, (5%) at 80 K obtained by pumping with an Argon ion laser at 2.41 eV (reproduced by permission of the American Physical Society from Rel. [32)). 

Fig. 0.5. IR absorption spectra of HC1 in different liquid solvents (a) in SF6 [16] (the triangles mark the positions of the rotational components in the resolved spectrum of the rarefied gas) (b) in He [15] (c) in CCU (the vertical lines mark the frequencies vj and the intensities of the Stark components of the linear rotator spectrum split by the electrical field of the cage)[17].

Fig. 10. IR absorption spectra of the species AuLi in various matrices 203).

Techniques are described which obtain the IR absorption spectra of species, either adsorbed or free In the electrode/electrolyte solution Interphase. Applications slanted towards topics relevant to electrocatalytic processes are discussed to Illustrate the capabilities of the methods In probing molecular structure, orientation and Interactions. 

Figure 6. IR absorption spectra of chlorinated PVC before and after laser irradiation at 488 nm for 0.1 s in air...

Fig. 24. (Left) VCD and IR absorption spectra of poly-Lys Pn ( unordered form) in ILO. (Right) o -Helix in CD3OD-D2O. From Yasui and Keiderling (1986)./. Am. Chem. Soc. 108,5576-5581. 1986, Reprinted with permission from American Chemical Society.

Infrared (IR) spectroscopy is commonly used to "fingerprint" materials by comparing the IR absorption spectra of unknowns against reference standards. 

IR absorption spectra were superimposable onto those of the physical mixtures of the respective homopolymers. The molar ratio of the poly(MMA) and polyethylene blocks, however, decreased as the Mn of the prepolymer increased, especially when it exceeded ca. 12 000 at which polyethylene began precipitating as fine colorless particles. It is noteworthy that smooth block copolymerization of ethyl acrylate or methyl acrylate to the growing polyethylene chain (Mn = 6 600-24 800) can be realized by the sequential addition of the two monomers. 

Fig. 4. IR absorption spectra for (a) acceptor-H and (b) acceptor-D complexes in Si. Spectra were measured near liquid He temperature. [Reprinted with permission from the American Institute of Physics, Stavola, M., Pearton, S.J., Lopata, J. and Dautremont-Smith, W.C. (1987). Appl. Phys. Lett. 50, 1086.]...

IR absorption spectra of the 1903 cm-1 stretching mode of the B—H complex were measured under stress (Bergman et al., 1988b) at low temperature where subsequent studies have found that the complex is static (Stavola et al., 1988b). Spectra are shown in Fig. 16 for different stress... 

Figure 1. IR absorption spectra of 4-allyloxystyrene (a) uncured monomer (b) after 10 s UV exposure with cationic photoinitiator (c) after UV exposure and heating at 200°C for 1 hour and (d) after an additional 16 hours heating at 200°C.

The IR absorption spectra of the PPV precursor LB film before and after the heat treatment are depicted in Fig.23. After the heat treatment, absorptions assigned to trails -vinylene CH out-of-plane bending and trans-CH stretching are observed at 963 cm1 and around 3022 cm 1, respectively. The appearance of the modes is an evidence that the PPV structure was formed by the thermal elimination of the sulfonium group in the LB film. On the other hand, absorptions at 2922 cm 1 and 2854 cm1, which are assigned to aliphatic chains of the anionic amphiphile, disappear after the heat treatment. It is turned out that almost all of the anionic amphiphile molecules were removed during the heat treatment. 

The reaction of the p-nitrophenyl esters with the polymer (4) was studied in dimethyl sulfoxide ( DMSO ) solution in the presence of triethylamine at 25°C. The poly-L-lysine derivatives obtained have different IR absorption spectra from those of the starting compounds, and have absorptions assigned to the nucleic acid bases. Poly( e,N-Ade-L-lysine )(5) was soluble in DMSO and ethylene glycol, and also in water below pH 3, where it was present as a protonated form. In dimethylformamide (... 

Microcantilever sensors can be operated in modes in which receptor-based coatings are not needed for example, deflagration of adsorbed energetic molecules can induce a measurable response [10]. Since cantilevers can be made extremely sensitive to temperature using bimaterial effect, calorimetric methods can be carried out on cantilevers with adsorbed molecules [11, 12], Exposing the temperature-sensitive cantilevers with adsorbed species to different infrared (IR) wavelengths in a sequential fashion creates mechanical signatures that mimic the IR absorption spectra of the analyte [13]. 

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