Rare gases Xenon

The rare gas xenon contains two NMR-sensitive isotopes in high natural abundance Xe has a spin of 1/2 and Xe is a quadrupolar nucleus with a spin of 3/2. The complementary NMR characteristics of these nuclei provide a unique opportunity for probing their environment. The method is widely applicable because xenon interacts with a useful range of condensed phases including pure liquids, protein solutions, and suspensions of lipid and biological membranes. It was found that the range of chemical shifts of Xe dissolved in common solvents is = 200 ppm, which is 30 times larger than that found for in methane dissolved... 

If there is any chance to isolate organometallic compounds of the lan-thanoides in the oxidation state Ln ", it should be possible in the case of cerium because of the electron configuration of the rare gas xenon for the ion The first paper published in 1971 reported the success-... 

In the case of a PPI, the coil is replaced by small permanent magnets placed on both sides of the thruster. The insulating walls are made of alumina or BNSi02. The nominal version can generate a thrust force of between 1 and 15 mN. The gas used is a rare gas (xenon or krypton). In the... 

The molal diamagnetic susceptibilities of rare gas atoms and a number of monatomic ions obtained by the use of equation (34) are given in Table IV. The values for the hydrogen-like atoms and ions are accurate, since here the screening constant is zero. It was found necessary to take into consideration in all cases except the neon (and helium) structure not only the outermost electron shell but also the next inner shell, whose contribution is for argon 5 per cent., for krypton 12 per cent., and for xenon 20 per cent, of the total. 

Fig. 3.6. The spectral moment y as function of the product of densities, for various rare-gas mixtures at room temperature only one density was varied for each system the neon densities were fixed at 77, 31 and 46.5 amagats for the neon-argon, neon-krypton and neon-xenon mixtures, respectively and the krypton and xenon densities were fixed at 152 and 50 amagats, respectively, in their mixtures with argon. The departures from the straight lines seen at intermediate densities squared indicate the presence of many-body interactions. Reprinted with permission by Pergamon Press from [329].

RARE GAS. Any of the six gases composing the extreme right-hand group of the periodic table, namely helium, neon, argon, krypton, xenon, and radon. They are preferably called noble gases or (less accurately) inert gases. The first three have a valence of 0 and are truly inert, but the others can form compounds to a limited extent,... 

A common result of all the experiments is that most molecules quench the alkali resonance radiation very effectively with total cross sections ranging from 10 A2 to over 200 A2. However, if the molecule BC is replaced by a rare-gas atom, the quenching cross sections become very small at thermal energies. They are probably below 10 2 A2 for quenching by helium, neon, argon, krypton, and xenon.55 The latter result is easily understood in terms of Massey s adiabatic criterion.67 If Ar is a characteristic interaction range, v the impact velocity, and AE the energy difference between initial and final electronic states E(3p) and E(3s), respectively, then we must have a Massey parameter... 

Tolstikhin, I. N., O Nions, R. K. (1994) The Earth s missing xenon A combination of early degassing and of rare gas loss from the atmosphere. Chem. Geol., 115, 1-6. 

Zangwill and Soven [10] have calculated the photoabsorption spectrum of rare-gas atoms from the frequency-dependent KS equations (156)-(157) within the ALDA. As an example for the quality of the results we show, in Fig. 3, the photoabsorption cross section of Xenon just above the 4d threshold. The agreement with experiment is remarkably good. Results of similar quality have been achieved for the photoresponse of small molecules [156, 157]. 

Pulse-probe studies using the Laser Electron Accelerator Facility (LEAF) at Brookhaven National Laboratory have revealed changes in optical absorption occurring on the picosecond time scale in rare gas fluids. In xenon, excimers are formed which absorb in the visible and near infra-red as shown in Fig. la. The absorption grows in during the first 50 picoseconds [see Fig. 1(b)].This growth is concomitant with ion recombination that leads first to excited atoms, reaction 1(a), which immediately form excimers, Xe, because of the high density of xenon. 

The rare gas excimers readily transfer energy to various additives. Rates for transfer to nitrogen and hydrogen in krypton are known at 1 atm. Because excimer species have strong absorptions in the visible region, it is necessary to quench them when studying reactions of other intermediates by absorption spectroscopy. Ethane has been shown to be convenient for this purpose. The rate constant for excitation transfer from excimers to ethane in xenon was measured by the pulse-probe technique to be 3.4 x 10 ° molal s at pressures near 50 bar. Thus, addition of a small concentration of ethane can be used to reduce the absorption due to excimers to a small level at nanosecond times. 

Evidence that clustering of rare gas atoms occurs around ions comes from (a) ion mobility measurements, and (b) volume changes occurring on electron attachment to solutes. The mobility of positive ions in xenon decreases with increasing pressure and at pressures near 100 bar is 1.3 X 10 cm /Vs [see Fig. 3(a)] near room temperature. An estimate of the size of the cluster moving with the ion may be obtained from such data using the Stokes equation. 

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