Cesium bromide region

A recent publication [ ] reported on the infrared spectra of over 200 inorganic compounds in the cesium bromide region. Characteristic frequencies are listed for inorganic ions in the 300 to 700... 

The infrared spectra of many inorganic salts have been determined in the sodium chloride region [ ] and in the cesium bromide region [ ]. From these studies, several characteristic frequencies for polyatomic ions have been found. These frequencies have proved useful in qualitative inorganic analysis. 

Characteristic Absorption Frequencies for Several Polyatomic Inorganic Anions in the Sodium Chloride and Cesium Bromide Regions... 

The present discussion will be limited to a considerable extent to those regions of the far infrared which can be studied with commercially available double-beam infrared instruments and which arise primarily from vibrational modes of the molecules. For the most part this includes only a small portion of the far-infrared region, namely, the potassium and cesium bromide regions, but covers the region which is of the most interest in analytical applications. This is true because most of the low-lying vibrational frequencies occur... 

SPECTRA-STRUCTURE CORRELATIONS FOR ALIPHATIC AND AROMATIC HYDROCARBONS IN THE CESIUM BROMIDE REGION... 

The material of the prism is important in infrared spectroscopy, since it must be transparent to infrared light. The material most frequently used for analysis in the middle wavelength region is sodium chloride. Prism materials for the analysis of short and long wave infrared light are usually potassium bromide, cesium bromide, and cesium iodide. 

Polymeric materials such as rubber, resins and plastics are recorded as pyrolyzates, films, or in solution. The spectra of liquid samples are obtained in cesium bromide or iodide and KRS-5 cells. Since the latter cells give interference patterns and reflect approximately 30% of the incident beam at each surface, cesium bromide or iodide cells are more desirable for work in the long-wavelength region. The cesium bromide and iodide plates are soft and easily polished with paper towels. In an air conditioned room corrosion by atmospheric water vapor is not very serious, and with careful handling the cesium bromide cells are as easy to work with as potas-... 

These considerations also explain the occurrence of cases of dimorphism involving the sodium chloride and cesium chloride structures. It would be expected that increase in thermal agitation of the ions would smooth out the repulsive forces, that is, would decrease the value of the exponent n. Hence the cesium chloride structure would be expected to be stable in the low temperature region, and the sodium chloride structure in the high-temperature region. This result may be tested by comparison with the data for the ammonium halides, if we assume the ammonium ion to approximate closely to spherical symmetry. The low-temperature form of all three salts, ammonium chloride, bromide and iodide, has the cesium chloride structure, and the high-temperature form the sodium chloride structure. Cesium chloride and bromide are also dimorphous, changing into another form (presumably with the sociium chloride structure) at temperatures of about 500°. 

IR Spectra. A Perkin-Elmer 337 recording IR spectrophotometer was used routinely to obtain IR spectra at 4000-400 cm" For this region, the samples were prepared as Nujol mulls pressed between potas-sum bromide plates or as solutions in matched liquid cells (0.1-mm path length) with potassium bromide windows. The far-IR spectra were obtained on a Perkin-Elmer 457 grating IR spectrophotometer. Samples for this region were prepared as Nujol mulls and pressed between cesium iodide plates. 

Figure 14.6. Phase diagrams of lyotropic mixtures (temperature versus amphiphile concentration), (a) Hexadecyltrimethylammonium bromide (CTAB)/water, after [50]. L isotropic micellar solution hexagonal phase V bicontinuous cubic phase L lamellar phase C several heterophasic regions containing crystalline components Nc nematic phase of rod-like micelles, (b) Cesium pentadecafluorooctanoate (CsPFO)/water, after [8].

Monochromators employing prisms for dispersion use a Littrow 60° prism plane mirror mount. Midinfrared instruments employ a sodium ehloride prism for the region from 4000-650 cm (2.5-15.4 pm), a potassium bromide or cesium iodide prism and optics extend the useful speetrum to 400 em (25 pm) or 270 em (37 pm), respectively. Quartz monochromators, designed for the ultraviolet visible region, extend their eoverage into the near infrared to 2500 cm (4 pm). 

---