Infra-red region

Most dichroism studies of oriented polymers have so far been made in the infra-red region, where the frequencies of absorption peaks measured 

In the case of amorphous polymers, and the amorphous regions of partially crystalline polymers, the polymer chain conformation is no longer uniform or repetitive along its length. Details of the local chain 

THEORETICAL GH VALUES FOR VARIOUS CONFORMATIONS IN AMORPHOUS POLYETHYLENE AND PROPOSED IR ASSIGNMENTS 

Conforma tion Transition moment direction Gi Proposed IR frequency Assignment Ref. 

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When a substance is transparent to visible light, such as single crystals of simple inorganic solids which do not contain uansition metal ions, or some glasses, anotlier significant component in the thermal conductivity is the transmission of photons in the infra-red region, which becomes more important with... 

Thus the x-ray data do not decide between this structure and a truly plane structure. Evidence from another source is at hand, however. A plane C03= or N03 ion should show three characteristic fundamental vibrational frequencies. These have been observed as reflection maxima in the infra-red region. But two of the maxima, at 7 m and 14m, are double,27 and this doubling, which is not explicable with a plane configuration, is just that required by a pyramidal structure, the separation of the components giving the frequency of inversion of the pyramid.28... 

A laser is a source of monochromatic radiation available principally in the visible and infra red regions. Light from a laser has several properties... 

The solids may be examined as alkali halide mixture and usually NaCl is used because it is transparent throughout the infra red region. Potassium bromide also serves the purpose well. The substance under examination should also be perfectly dry because water absorbs strongly at about 3710 cm 1 and also at 1630 cm-1. 

Near infra-red reflectance spectroscopy was first used by Norris and Hart [54] for the determination of moisture, oil and fat in cereal products. A number of instrument companies, notably Technicon, have developed commercial instruments. The instrument replaces a series of chemical procedures by a signal measurement in each of six infra-red regions and reference to a suitable computer calibration. Such an approach offers... 

Three kinds of phenomenon play their part in the production of these band spectra, electronic changes within the molecule, vibration of the atoms in the molecule, and rotation of the molecule as a whole. The electronic processes give rise to emission or absorption in the visible and ultra-violet regions, the intra-atomic vibrations to bands in the short infra-red region at wave-lengths of the order of several /x, and the molecular rotations to bands in the far infra-red at wave-lengths of the order 100 /. ... 

The temperature coefficient of the reaction is still given by the Arrhenius equation. It is reasonable to assume that the velocity constant of the reaction is proportional to the radiation density. Now chemical heats of activation correspond to frequencies in the short infra-red region, and for these values of v the term ehvlkT in Planck s equation is large in comparison with unity. The expression for Uy thus reduces to... 

Photo-electric effect no yes liquids, powders, granular solids. Electromagnetic signal in visible light or infra-red region of electromagnetic spectrum is sensed by photo-electric cell. Beam is attenuated by liquids and cut off by solids. Liquids can transmit or reflect the beam. 

Fic. 6.42. Absorbance spectra of wet and dry polyalkylene glycol ether (brake fluid) in the near infra-red region of the electromagnetic spectrum 5 ... 

Formic acid H.COOH and acetic acid CH3.COOH were studied in the crystalline state by Carlson, Witkowski and Fateley, 66> in the far infra-red region, while Fukushima and Zwolinski, 67> gave a normal coordinate calculation of acetic acid dimers (CH3.COOH)2 the acetate ion in Li(CH3.C00).2H20 was studied by Cadene 168>, while DiLauro, Califano and Adembri 169> studied the crystal spectra and normal modes of the anhydrides of maleic and succinic acids in polarized light. 

The infra red region between 4000 and 200 cm-1 can be divided roughly into five regions ... 

Infra-red absorption spectra. For a long time the experimental difficulty of working with nitric acid in the infra-red region due to corrosion of the cells by nitric acid hindered examination of the infra-red absorption spectrum of nitric acid. Originally therefore, only the near infra-red region was studied. 

In the infra-red region the nitro group produces two bands of high intensity one near 6.4p (1563 cm 1), which characterizes asymmetric vibrations of the... 

Water-vapour exerts a distinct selective action on light,6 the effect of atmospheric moisture being detectable spectroscopically m sunlight. It manifests absorption in the infra-red region, and the a absorption band is interesting as being the one by which the presence of water vapour on Mars was first determined by Slipher in 1908.7... 

In some cases such information is readily interpreted and understood. For example, carbon monoxide adsorbed on a metal will show strong carbonyl absorptions (v(CO)) in the infra-red region similar to those found in molecular metal carbonyl complexes (See Al.1.3). The exact positions of the absorption, the number of bands and their shapes, can be correlated with the type of binding (to one, or more, metal atoms) and even to the strength of the bonds. 

The infra red region has been divided into three parts ... 

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