Xenon Equilibrium

Because it would be difficult to compare isothermal adsorption results for multiphase samples, the studies were restricted to NaY zeolite and the compound for which R = 0.05. For both solids, the logarithmic representations for the relation log N = f (log P), where N is the number of adsorbed xenon atoms per gram of dehydrated zeolite and P is the xenon equilibrium pressure, are straight lines. The line for the sample with R = 0.05 is below that of NaY zeolite (Figure 3). The log N value extrapolated to zero abscissa is smaller, and the slope is only a little larger. 

Xenon Adsorption Experiments. Gaseous xenon was co-adsorbed onto the samples on a vacuum manifold the xenon equilibrium pressure was measured by an absolute-pressure transducer (MRS Baratron) capable of measuring pressure with accuracy 0.1 torr. The adsorption isotherms of the co-adsorbed xenon in the samples were measured volumetrically at 22 °C. 

Figure 7 gives the Sxe-NMR spectra obtained from xenon adsorbed at 300 K on a sample containing NaY and RbNaX zeolites. These zeolites have the same framework structure and have been studied extensively by Ito et al.[ 4 ] The two peaks in Fig. 7-(a), (I) 144 and (II) 89 ppm, correspond to xenon adsorbed in RbNaX and NaY zeolites, respectively. RbNaX has a higher xenon chemical shift than NaY at the same xenon equilibrium pressure due to its higher cation concentration inside the zeolite and, more importantly, to much higher polarizability of Rb than Na+ cations. 

Xenon peaking Xenon oscillation transient Xenon equilibrium Xenon d... 

T. Y. Makogon, A. P. Mehta, and E. D. Sloan, Jr. Structure H and structure I hydrate equilibrium data for 2,2-dimethylbutane with methane and xenon. J Chem Eng Data, 41(2) 315-318, March-April 1996. 

Xenon hexafluoride is known to exist in condensed phases as an equilibrium mixture that can be shown as... 

Tautomerism. Owing to the presence of the guanidine moiety in the structure of tegaserod, the three tautomers shown below are possible. Tautomer 6a is assigned to the solid state of tegaserod, as confirmed by X-ray structure analysis of the 5-0-benzyl derivative. In solution, 6b and 6c also exist in equilibrium depending on the experimental conditions. For instance in DMSO, the solvent used to measure NMR spectra, 6b is preferred. Tautomer 6c is formed in methanol after exposure to xenon light, and from this solution the tautomer can even be separated by HPLC. 

In this paper we present the first application of the ZORA (Zeroth Order Regular Approximation of the Dirac Fock equation) formalism in Ab Initio electronic structure calculations. The ZORA method, which has been tested previously in the context of Density Functional Theory, has been implemented in the GAMESS-UK package. As was shown earlier we can split off a scalar part from the two component ZORA Hamiltonian. In the present work only the one component part is considered. We introduce a separate internal basis to represent the extra matrix elements, needed for the ZORA corrections. This leads to different options for the computation of the Coulomb matrix in this internal basis. The performance of this Hamiltonian and the effect of the different Coulomb matrix alternatives is tested in calculations on the radon en xenon atoms and the AuH molecule. In the atomic cases we compare with numerical Dirac Fock and numerical ZORA methods and with non relativistic and full Dirac basis set calculations. It is shown that ZORA recovers the bulk of the relativistic effect and that ZORA and Dirac Fock perform equally well in medium size basis set calculations. For AuH we have calculated the equilibrium bond length with the non relativistic Hartree Fock and ZORA methods and compare with the Dirac Fock result and the experimental value. Again the ZORA and Dirac Fock errors are of the same order of magnitude. 

Cassel and Neugebauer (18) investigated the adsorption of some of the rare gases on mercury over a range of temperatures by surface tension measurements. They found that the curves for surface pressure against gas pressure were almost linear and it is possible to interpolate their results to the standard state ir = 0.0608 dynes/cm., obtaining the pressure p0 in equilibrium with a film at this surface pressure. The thermodynamic quantities for the adsorption of xenon are given in Table IV ... 

The quantities of xenon adsorbed by each Pn sample are plotted against the equilibrium pressure, in a double logarithmic scale (Fig.1). All intermediate phases show fully linear isotherms over the pressure range investigated (10 to 900 Torr). No saturation is observed below 900 Torr, even for Pq. 

As mentioned in sections 1.2.2.2 and 1.2.3.2, the photochromic reactions of spirobenzopyran and spironaphthoxazines show a marked solvent dependency and this is also the case with benzo and naphthopyrans. Consequently, spectral data collected from the literature is only comparable within any one study or where the same solvent has been used. This accounts for any discrepancies between one set of results and any other one listed in this and related sections of this chapter. The data normally quoted when discussing the properties of photochromic materials relate to the absorption maximum (2. ) of the coloured state, the change in optical density (absorbance) on exposure to the xenon light source (AOD) and the fade rate which is the time in seconds for the AOD to return to half of its equilibrium value. 

Fig. 17.2 Equilibrium pressures of xenon fluondes as a function of temperature. Initial conditions ...

Equilibrium pressure 400 torr. Chemical shifts are given in ppm from xenon gas at zero pressure. 

In cases where the annihilation rate, and hence Zef[, is a rapidly varying function of the positron energy, as with xenon (Schrader and Svetic, 1982), the simplification introduced above is not valid and the solution to equation (6.15) must be used. The functional form for f(v) given in equation (6.17) was used by Campeanu and Humberston (1977b) to investigate the variation of the equilibrium value of (Zeff) with electric field and temperature, and their results for the former are shown in Figure 6.3. 

Barrer, R. M., Edge, A. J. V. (1967) Gas hydrate containing argon, krypton, and xenon Kinetics and energetic of formation and equilibrium. Proc. Roy. Soc., London, A300, 1-24. 

Xenon was adsorbed in a volumetric apparatus at ambiant temperature. Adsorption equilibrium was reached after 30 minutes. 

This big influence of temperature on the equilibrium is a consequence of the large change in translational entropy in going from reactants to products [15]. Agf+iv) is also able to oxidize perfluoroolefins such as perfluoropropene the ionization potential of which is much lower (7= 10.62 eV) [29] than those of xenon or oxygen. The observed formation of perfluoropropane (quantitatively) is in accord with the cation being attacked by F, followed by a second one-electron oxidation and F attack. The hierarchy of powerful oxidizers could be written as follows (see also Sections 4.2.2.5 and 4.2.2.6). 

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