IR region

Trioctahedral micas. In a detailed calorimetric study of phlogopite by Clemens et al. 

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Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy. Attenuated total redectance (atr) ftir spectroscopy is based on the principle of total internal redection (40). Methods based on internal redection in the uv and visible regions of the spectmm are also common in addition to those in the ir region. The implementation of internal redection in the ir region of the spectmm provides a means of obtaining ir spectra of surfaces or interfaces, thus providing moleculady-specific vibrational information. 

Laser sources that emit in the mid-ir region of the spectmm (2—5 -lm) are useful for detection of trace gases because many molecules have strong absorption bands in that region. Other appHcations include remote sensing and laser radar. Semiconductor lead—salt (IV—VI) lasers that operate CW at a temperature of 200 K and emission wavelength of 4 p.m are commercially available however, they have relatively low output powers (<1 mW) (120). 

Optical Coatings. Thin surface coatings are appHed to optical components to improve performance. Wideband antireflection coatings for the visible and ir regions need materials with a refractive iadex of for the best efficieacy. Cerium fluoride, a stable material resistant to humidity damage, has a suitable iadex, 1.63 ia the visible, 1.59 ia the iafrared, and is transparent over the range 0.5 p.m to 5 p.m. It is one of the compounds used to build up the multilayers deposited on lenses, sensors, and the like. 

It helps in remembering the position of specific IR absorptions to divide the IR region from 4000 to 400 cm-1 into four parts, as shown in Figure 12.15. 

Aldehydes and ketones show a strong C=0 bond absorption in the IR region from 1660 to 1770 cm-1, as the spectra of benzaldehj7de and cyclohexanone demonstrate (figure 19.17). In addition, aldehydes show two characteristic C-H absorptions in the range 2720 to 2820 cm-1. 

Diverse series of diphenyl sulphoxide (DPSO) complexes of Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ca(II), Al(II) and Mg(II) with various large anions have been reported187-191. The complexes have the general formula M(DPSO)6(Anion) where M is the metal cation. The reflection spectra in the visible and near-IR region indicate an octahedral configuration around the metal ion surrounded by the DPSO molecules. Comparison with the spectra of DMSO complexes shows that they have almost identical structures. IR spectra indicate that the oxygen atom in the sulphinyl group is the donor atom in all these complexes. 

In contrast, when a THF-acetonitrile solution of [26+jClOj or [113+JC104 was added to the THF solution of K+[2 ], the deep green colour of carbanion [2 ] persisted. After evaporation of the solvent, purification of the residue yielded a dark green salt, [26+2 ] or [113+2 ] (Scheme 3), the IR spectra (KBr disk) of which consisted of the absorptions of [2 ] and [26+] or [113+] superimposed. The visible-near IR region... 

Due to the absorption band of the colored form of spiroindolinoben-zothiopyrans in the near IR region, they have been used in the optical erasable recording disks.89,100,101 The principle of optical erasable recording system using photochromic spirobenzothiopyran is explained as follows. 

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