Noble gas trapping

Crystal structures of a few fullerenes containing endohedral atoms have been recently solved (apart from the noble gas trapping Kr C60,22a the metal atoms containing Sc3 N C78,22b Sc3 N C80 and Sc2 ErN C80>22c Y C82,22d Sc C82,22e Er2 C82,22f Sc3 Cs2,228 Sc2 C84,22h Sc2 C2 C84,221), but unfortunately their electrochemical behaviour is not known. Electrochemical information is also limited for those endohedral complexes which lack definitive structural characterization.23... 

Ion implantation is another common noble gas trapping mechanism in nature. For example lunar soils are implanted by solar emission particles that essentially consist of lighter noble gases. A few laboratory experiments have been carried out with the hope that experiments may be relevant to incorporation of noble gases in early solar... 

Frick, U., Mack, R., Chang, S. (1979) Noble gas trapping and fractionation during synthesis of carbonaceous matter. Proc. Tenth Lunar Planetary Science Conf., 2, 1961-73. 

Kothari, B. K., Marti, K., Niemeyer, S., Regnier, S., Stephens, J. R. (1979) Noble gas trapping during condensation A laboratory study (abstract). In Lunar and Planetary Science, vol. X, pp. 682 1. Houston Lunar Planetary Institute. 

Crystallization of solutions of quinol [p-dihydroxybenzene, p-C6H4(OH)2] in water or alcohol under pressure of 10-40 atm of, say, krypton, produces crystals, often up to 1 cm in length, which are readily distinguishable from the crystals of ordinary quinol (a-quinol), even visually. These crystals contain the noble gas trapped in the lattice of -quinol. When the crystals are dissolved in water, or heated, the gas is released. The crystals are stable at room temperature and can be kept for years. 

Niemeyer S, Marti K (1981) Noble gas trapping by laboratory carbon condensates. Proc 12th Lunar Planet Sci Conf,p 1177-1188... 

The molecular constants that describe the stnicture of a molecule can be measured using many optical teclmiques described in section A3.5.1 as long as the resolution is sufficient to separate the rovibrational states [110. 111 and 112]. Absorption spectroscopy is difficult with ions in the gas phase, hence many ion species have been first studied by matrix isolation methods [113], in which the IR spectrum is observed for ions trapped witliin a frozen noble gas on a liquid-helium cooled surface. The measured frequencies may be shifted as much as 1 % from gas phase values because of the weak interaction witli the matrix. 

Probably the most familiar of all clathrates are those formed by Ar, Kr and Xe with quinol, l,4-C6H4(OH)2, and with water. The former are obtained by crystallizing quinol from aqueous or other convenient solution in the presence of the noble gas at a pressure of 10-40 atm. The quinol crystallizes in the less-common -form, the lattice of which is held together by hydrogen bonds in such a way as to produce cavities in the ratio 1 cavity 3 molecules of quinol. Molecules of gas (G) are physically trapped in these cavities, there being only weak van der Waals interactions between... 

Phenylisosilacyanide is produced either by irradiation of triazidophenyl-silane in matrix isolation or by pyrolysis followed by trapping in noble gas matrix (Eq. 3). The reaction with /-butanol leads to the expected product6 ... 

The application of matrix isolation to organometallic chemistry has been extensively described elsewhere (4,5,6,7). Two methods have generally been employed. In the first, based on G.C. Pimentel s original development, the solid matrix environment is a frozen noble gas - usually Ar - at 10-20K and the unstable fragment is generated either by photolysis of a parent molecule already trapped in the matrix, or by cocondensation from the gas phase. In the... 

The nitrogen complex had already been synthesized in a solid matrix, but its decomposition kinetics and its further photolysis could be studied only in solution. The liquid noble gas technique is superior to the solid matrix technique, especially for the synthesis of multiple substituted chromium carbonyl nitrogen complexes. Their IR spectra were extremely complex in matrices, due to "site splittings" which arise when different molecules are trapped in different matrix environments /18/. 

The noble gas elements act as a record of the deposited material because they are essentially chemically inert and are also trapped within the ice of comets and meteorites. The late-heavy bombardment era must have affected both the Earth and the Moon similarly so an estimate of the collision frequency may be obtained by using the record of impacts on the Moon s surface. The collision rate calculated... 

He is found in natural gas deposits principally because alpha particles are produced during natural radioactive decay processes. These alpha particles are 4 He nuclei they obtain two electrons from the surrounding material to become helium atoms. This gaseous helium then accumulates with the natural gas trapped beneath the earth. Although other noble gases are produced by radioactive decay—notably 40 Ar—they are not produced in the large quantities that helium is. 

Noble gas abundances in lunar soils and chondrites, (a) Elemental abundance patterns for trapped solar wind in lunar soils, normalized to solar system abundances, (b) Elemental abundance patterns for planetary trapped noble gases, normalized to solar system abundances. This diagram is intended to illustrate patterns only vertical positions are arbitrary. Modified from Ozima and Podosek (2002). 

Table 10.2 Trapped planetary noble gas components in meteorites ...

McKean 182> considered the matrix shifts and lattice contributions from a classical electrostatic point of view, using a multipole expansion of the electrostatic energy to represent the vibrating molecule and applied this to the XY4 molecules trapped in noble-gas matrices. Mann and Horrocks 183) discussed the environmental effects on the IR frequencies of polyatomic molecules, using the Buckingham potential 184>, and applied it to HCN in various liquid solvents. Decius, 8S) analyzed the problem of dipolar vibrational coupling in crystals composed of molecules or molecular ions, and applied the derived theory to anisotropic Bravais lattices the case of calcite (which introduces extra complications) is treated separately. Freedman, Shalom and Kimel, 86) discussed the problem of the rotation-translation levels of a tetrahedral molecule in an octahedral cell. 

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