Solid-state materials, xenon

Organic solids have received much attention in the last 10 to 15 years especially because of possible technological applications. Typically important aspects of these solids are superconductivity (of quasi one-dimensional materials), photoconducting properties in relation to commercial photocopying processes and photochemical transformations in the solid state. In organic solids formed by nonpolar molecules, cohesion in the solid state is mainly due to van der Waals forces. Because of the relatively weak nature of the cohesive forces, organic crystals as a class are soft and low melting. Nonpolar aliphatic hydrocarbons tend to crystallize in approximately close-packed structures because of the nondirectional character of van der Waals forces. Methane above 22 K, for example, crystallizes in a cubic close-packed structure where the molecules exhibit considerable rotation. The intermolecular C—C distance is 4.1 A, similar to the van der Waals bonds present in krypton (3.82 A) and xenon (4.0 A). Such close-packed structures are not found in molecular crystals of polar molecules. 

Xenon Xe)(I = 1/2). The authors report the variation of Xe chemical shift 6 vs. the pore size, the temperature and the xenon pressure of xenon adsorbed on mesoporous materials prepared in different synthesis conditions. The xenon and fluorine magnetic shielding tensors, a, of XeF2 are characterized using solid-state Xe and F NMR spectroscopy and nonrelativistic and spin-... 

Solid State Lasers. The first successful laser, and one that is still used, is a three-level device in which a ruby crystal is the active medium. Ruby is primarily AhO, but contains approximately 0.05% chroraium(III) distributed among the aluminum(III) lattice sites, which accounts for the red coloration. The chromium(III) ions are the active lasing material. In early lasers, the ruby was machined into a rod about 4 cm long and 0.5 cm in diameter. A flash tube (often a low-pressure xenon lamp) was coiled around the cylinder to produce intense flashes of light (A = 694.3 nm). Beeause the flashlamp was pulsed, a pulsed beam was produced. Continuous-wave (CW) ruby sources are now available. 

Rare earth laser action has been obtained for two groups of liquids metallo-organic and inorganic aprotic liquids. The first group are chelate lasers and are reviewed by Lempicki and Samelson (1966) research on aprotic materials and systems for high-power, pulsed liquid lasers are reviewed by Samelson and Kocher (1974). Stimulated emission in both liquids occurs between 4f states of trivalent rare earths. Optical pumping is via xenon-filled flashlamps in optical cavities and resonators similar to those used in solid-state lasers. Rare earth liquid lasers have only been operated pulsed. 

Xenon and platinum hexafluoride interact at room temperature to form a red solid of composition Xe(PtF6)a where x lies between 1 and 2. That the platinum is present in the -f-S oxidation state, no matter what the composition of the adduct, is indicated by the preparation of alkali metal hexafluoroplatinates(V) from material of composition XePtFe and Xe(PtF6)2. Material containing more than one mole of platinum hexafluoride per gram atom of xenon combines with more xenon at 130° to approach the composition XePtFe. 

The diamagnetic brick-red solid of composition XePt2Fio, formed along with xenon tetrafluoride in the pyrolysis of Xe(PtF6)i.8, contains the platinum in the -f-4 oxidation state, since interaction of the material with cesium fluoride in iodine pentafluoride gives a yellow product. X-ray powder photographs of which... 

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