Saturated Xenon

Fig. 9. (A) and (B) Absorbance difference spectrum of Cf. aurantiacus reaction centers measured 10 ms after a 13-/rs saturating xenon flash was applied sample absorbance at 865 nm was 9x10. (C) and (D) are the absorbance difference spectra measured the same way as in (A) and (B), except that the reaction-center sample contained Asc and PMS as an exogenous reductant. The dashed spectrum in (C) is the in vitro difference spectrum of vitamin K-1 in methanol obtained by EJ Land by pulse radiolysis. Figure source Vasmel and Amesz (1983) Photoreduction of menaquinone in the reaction centers of the green photosynthetic bacterium Chloroflexus aurantiacus. Biochim Biophys Acta 724 119-121.

The staff found that in 1968 a study was done by SRL to determine xenon oscillation dependence on various reactor parameters (Reference 16). This study indicated that xenon oscillation depends primarily on the neutron flux level, spectrum, and shape the neutron migration area reactor dimenstons saturation xenon worth and the temperature coefficient of reactivity. Of these parameters, only the neutron flux level and shape and the temperature coefficient were found to represent viable design variables. 

In other applications of CT, orally administered barium sulfate or a water-soluble iodinated CM is used to opacify the GI tract. Xenon, atomic number 54, exhibits similar x-ray absorption properties to those of iodine. It rapidly diffuses across the blood brain barrier after inhalation to saturate different tissues of brain as a function of its lipid solubility. In preliminary investigations (99), xenon gas inhalation prior to brain CT has provided useful information for evaluations of local cerebral blood flow and cerebral tissue abnormalities. Xenon exhibits an anesthetic effect at high concentrations but otherwise is free of physiological effects because of its nonreactive nature. 

Values extracted and in some cases rounded off from ttose cited in RaLinovict (ed.), Theimophysical Propeities of Neon, Ai gon, Kiypton and Xenon, Standards Press, Moscow, 1976. Ttis source contains values for tte compressed state for pressures up to 1000 bar, etc. t = triple point. Above tbe sobd line tbe condensed phase is solid below it, it is liquid. Tbe notation 5.646. signifies 5.646 X 10 . At 83.8 K, tbe viscosity of tbe saturated liquid is 2.93 X 10 Pa-s = 0.000293 Ns/ui . Tbis book was published in English translation by Hemisphere, New York, 1988 (604 pp.). 

Ewald22 studied this system at 150° and 155°K. These temperatures are above the critical temperature of pure nitrogen, 126°K, but he found that they are below the lower critical end point of the mixture. The saturated vapor pressure of the system was 50 atm at 150°K and 57 atm at 155°K. The mole fraction of xenon in the saturated gas (X in Figs. 5 and 9) was 0.035 and 0.045 at these temperatures, respectively. 

The apparatus used for studying the photoelectrochemical behavior (11) of the Ti02 film electrode is shown in Figure 5- Platinum plate of 35x25 mm and saturated calomel electrode (S.C.E.) were employed as a counter and a reference electrode, respectively. A 500 W Xenon lamp was used for illuminating the Ti02 electrode. 

Taylor and Jarman [1] observed SL spectra in the range of 280-740 nm from 2 M NaCl solutions saturated with argon, krypton and xenon sonicated at frequencies of 16 and 500 kHz. The spectra showed a continuum background with bands at about 310 nm and a peak of sodium D line, which exhibited appreciable asymmetric broadening, as shown in Fig. 13.2. The bands around 310 nm result from the A2L+ — X2n transition of OH radicals. The OH bands are quenched in salt solutions compared with those in water, which suggests the energy transfer reaction... 

Fig. 13.2 MBSL spectra from 2M-NaCl aqueous solution saturated with xenon at frequencies of 16 kHz (a) and 500 kHz (b). The sodium D lines exhibit asymmetric broadening [1] (Reprinted from the CSIRO Publishing. With permission)...

M. x 108M 1s 1 at 25°C, but may be appreciably lower in the solid state. In comparison k2 for oxygen competition for the alkyl radical is 2 x 109M-1s 1. Thus for air-saturated PPH ([02] 8 x 10-1,M)reaction7 will be protection against xenon irradiation was improved as compared to the parent piperidine by about 25, but the nitroxide itself was reduced to the 1 x 10 M level within the first lOOh and persisted at this level until brittle failure (7,) In contrast the parent amine is completely destroyed in the first lOOh of xenon exposure. 

In a first experiment a pressure of 2 bar of CO at — I00°C was applied to a saturated solution of n-BuLi in liquid xenon. Surprisingly, no free CO was detected, but a stretching vibrational mode of the carbonyl adduct of the lithium alkyl was observed at 2047 cm (triple-bonded CO group). Warming up to —30°C led to the appearance of a new v(CO) peak at 1635 cm (double-bonded CO group), while the IR band of the carbonyl adduct vanished. The new absorption was therefore attributed to the acyllithium compound, which also decomposed at slightly higher temperature (—20°C) (equation 1) . ... 

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. 

The behavior of nitrous oxide during irradiation seems quite unusual. Whereas, as an irradiation atmosphere, 18 types of well-known inorganic gases and 4 types of saturated hydrocarbon gases were tested previously, the species which evidently showed such a singular effect were limited to nitrous oxide and xenon. In the work reported here, three types of polymers having different types of molecular structure were examined, but examination showed many points of similarity in the behavior of nitrous oxide. 

Xenon Adsorption Isotherms and 129Xe NMR Measurements. Figure 1 displays the room temperature (22 °C) xenon adsorption isotherms of the coadsorbed xenon for the three different zeolite samples loaded with various amounts of benzene. A consistent decrease of adsorption with increasing 6 was found for each benzene/zeolite system. By comparing the slope at low xenon pressures, i.e. in the Henry s Law region, we obtained for the adsorption strength NaX(1.23) > NaY(2.49) > NaY(2.70). Moreover, the saturation benzene concentration in faujasite-type zeolites with different Si/Al ratios follows the relation NaX(1.23) < NaY(2.49) < NaY(2.70). 

The saturated carbon atom can be functionalized by xenon difluoride in various ketones and diketones where, beside a-mono and a-difluoro ketones, the formation of rearranged products can also be observed however, the course of reaction depends strongly on the catalyst used22-24 (Scheme 5). 

The fact that the slopes of the 6-plots for partially decoked samples are the same as those of the initial coked ones proves that under our regeneration conditions the internal micropore void volume is practically unchanged (this is confirmed by the quantities of xenon adsorbed at saturation (212K) which are virtually identical). Thus a large fraction of the carbonaceous residues (at least 50%) is located on the external surface of the crystallites. 

The observed krypton and xenon concentrations in each water source in the Rift Valley study were converted in this way to percent air saturation... 

Fig. 13.6 Percentage of air saturation of krypton and xenon for the Jordan Rift Valley waters. The values were obtained by dividing the measured amounts by those expected for water equilibrated with air at the temperature at which each sample was collected. All samples, except one, were found to be air supersaturated, indicating that the rare gases were retained under closed system conditions. Differences in duplicate samples are attributed to gas losses to the atmosphere prior to sampling (Mazor, 1975).

Fig. 13.8 Percent air saturation of krypton and xenon for warm springs in Swaziland (same spring numbers as in Fig. 13.7). All samples were oversaturated at the temperature of emergence (35-52 °Q, indicating the systems were closed (Mazor et al., 1974).

The explanation is that free air has been siphoned into the karstic water, in addition to the initial dissolved air. The solubility of the noble gases is smallest for helium and increases toward xenon. This should not be confused with Fig. 13.1, which was obtained by taking the solubility of each noble gas and multiplying it by its abundance in air (Table 13.1). (One can obtain the noble gas solubility for a selected temperature by dividing the respective values in Fig. 13.1 by the abundance values of Table 13.1). Free air is relatively richer in the less soluble gases, therefore its addition to already saturated water in the karstic springs causes (1) excesses over 100% saturation and (2) the excess pattern of Ne > Ar > Kr > Xe. 

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