Supercritical krypton

Pulse Radiolysis in Supercritical Krypton and Xenon Fluids... 

In supercritical krypton the formation of excimers has also been time resolved but the results contrast with those for xenon.As in xenon, electron-ion recombination should occur rapidly. Again, electrons remain hot for many nanoseconds in krypton and the mobility of hot electrons is in the range of 150 to 400 cm /Vs. This leads to a theoretical range for of 1.4 to 3.6 x 10 m" s" at a density of 0.48 g/cm. In pulse radiolysis studies using optical detection, the concentration of intermediates is around 0.5 to 1 pM, thus the first half-life for recombination of electrons with ions is less than 10 ps in krypton. What has been observed is that an excimer species (A), the... 

Suppes and McHugh studied the effects of different surfaces on the decomposition of cumene hydroperoxide in supercritical krypton, xenon, CO2, propane, and CHF2CI. They reported that the observed first-order rate constants were strongly dependent on the metals present. Gold and 316 stainless-steel surfaces gave larger rate constants than did Teflon-coated surfaces [68]. The authors also observed that the different SCF solvents influenced the reaction rate. 

A special type of TM ligands are the noble gas atoms argon, krypton, and xenon [61]. Although they are weak Lewis bases, TM complexes M(CO)sNg with M = Cr, Mo, W and Ng = Ar, Kr and Xe have been experimentally investigated in the gas phase as well as in the liquid phase and in supercritical C02 [62, 63], The M-Ng BDEs were estimated with... 

Fischer et al, [122] proposed a model to predict the adsorption isotherm of krypton in porous material at supercritical temperature. In their study, a model pore of infinite length is formed by concentric cylindrical surfaces on which the centers of solid atoms are located. The interaction between an adsorbate and an individual center on the pore wall is described by the LJ 12-6 theory, and the overall potential is the integral of this interaction over the entire pore surface. With thermodynamic relations, Fischer et al. obtained the functional dependence of the saturation adsorption excess and the Henry s law constant on the pore structure. The isotherm was then produced by the interpolation between Henry s law range and saturation range. They tested their theory with the adsorption of krypton on activated carbon. It was shown that, with information on the surface area of the adsorbent and thermodynamic properties of the adso bate, their model gives more than quantitative agreement with experimental data. If a few experimental data such as the Henry s law constant at one temperature are available, the isotherms for all temperatures and pressures can be predicted with good quality. 

Pfund DM, Darab JG, Frrlton JL, Ma YJ (1994) An XAFS study of strontium ions and krypton in supercritical water. J Phys Chem 98 13102-1310... 

Effects other than those of purely viscometric origin were seen to be significant in a schematic study by McHugh and co-workers of the free radical decomposition of cumene hydroperoxide [48], and subsequent oxidation of cumene (isopropyl benzene) [49, 50] in a range of supercritical and liquid solvents. The effective non-catalysed rate coefficients for cumene hydroperoxide decomposition in non-polarisable supercritical fluids (krypton, xenon) were greater than that for non-polar liquid cyclohexane, as expected a priori on the basis of viscosities. Yet, liquid 1-octene and 1-hexanol gave similar... 

Of all the compounds capable of becoming supercritical fluids under relatively moderate temperatures and pressures, supercritical carbon dioxide (CO2) is unique in that, unlike supercritical alkanes (ethane, propane, and n-butane), it is nonflammable and environmentally friendly. Supercritical noble gases, such as krypton and xenon, are benign but very expensive. Although water is environmentally friendly, the critical temperature of 374" C and pressure of 212 atm are much higher that those for CO2. 

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