Xenon polarizable

Neon and xenon are gases at room temperature, but both become liquids if the temperature is low enough. Draw a molecular picture showing the relative sizes and polarizabilities of atoms of neon and xenon, and use the picture to determine which substance has the lower boiling point. 

The dispersion forces that act between atoms of the noble gases depend on the polarizabilities of their electron clouds. The total electron counts for these atoms are 10 for neon and 54 for xenon. When two atoms approach each other, the smaller electron cloud of neon distorts less than the larger electron cloud of xenon, as a molecular picture illustrates ... 

We apply this technique to study the effect of the spin-orbit coupling on an NMR shielding tensor and the shielding polarizability of the xenon atom. The shielding polarizabilities are defined as the second derivatives of nuclear shielding constants with respect to an electric field E... 

Table 5. The NMR shielding constant and shielding polarizabilities of the xenon atom calculated at the Hartree-Fock level using the Drrac-Coulomb Hamiltonian (SR + SO), its spin-free version (SR) as well as the non-relativistic Levy-Leblond Hamiltonian. The shielding constant is given in ppm and shielding polarizabilities in ppm/(au field2) (1 a.u. field = 5.14220642X 10" V...

I would like to dedicate this paper to Jens Oddershede on his 60th birthday. I would like to thank Magdalena Pecul for suggesting an additional s -exponent in the basis set used for the calculation of the shielding polarizability of the xenon atom. 

Atomic xenon, with its large polarizability, has chemical shifts extremely sensitive to its physical surroundings. Using isotope Xenon-129 as a probe, Ito and Fraissard proposed [4] that the °Xe chemical shifts of xenon adsorbed on a zeolite can be written as... 

The dynamics of the molecules adsorbed in confined geometry is one of the most common and important research subject which has received much attention in the past few decades. Owing to the large polarizability and the chemical inert nature of the monoatomic xenon, the l29Xe NMR chemical shift is very sensitive to its environment and thus provides an ideal probe for the investigation of the structure of porous materials [1]. There have been numerous publications in this area since the pioneering works by Ito and Fraissard [2] and by Ripmeester [3], and several reviews have been attributed to related subjects [4-7]. Recent developments of the mesoporous MCM-41 materials [8] have also drawn intense attention due... 

Argon, krypton, and xenon have polarizabilities of 16.5, 25.4, and 41.3 X 10 26 cm.3, respectively. McDonald found that these gases produce shifts of 8, 16, and 19 cm.-1. Nitrogen, oxygen, and methane, which have polarizabilities of 17.6, 16.0, and 26.0 X 10-26 cm.3, produce shifts of 24, 12, and 32 cm.-1, respectively. McDonald interpreted these results as showing that the polarizability is not the only factor involved and that the frequency shifts depend on an additional factor related to the chemical nature of the adsorbed molecules. He concluded that the frequency shifts cannot be completely explained in terms of macroscopic dielectric properties. 

The xenon atom can therefore be used as a delicate probe to determine the number of surrounding water molecules and their orientations. These results demonstrate the sensitivity of the easily polarizable xenon electronic structure to the electrostatic properties of its surrounding and the great potential for achieving accurate interpretations of magnetic resonance parameters from imaging experiments with hyperpolarized xenon. 

The terms polar, apolar and dipolar are often used to describe solvents and other molecules, but there is a certain amount of confusion and inconsistency in their application. Dipolar is used to describe molecules with a permanent dipole moment, e.g. ethanol and chloroform. Apolar should be used rarely and only to describe solvents with a spherical charge distribution such as supercritical xenon. All other solvents should, strictly speaking, be considered polar Therefore, hexane is polar because it is not spherical and may be polarized in an electric field. This polarizability is important when explaining the properties of such solvents, which do not have a permanent dipole and give low values on most polarity scales. Therefore, they are widely termed non-polar and, although... 

HCl in liquid xenon at T 185° K. has been studied (29). A spectrum consisting of three broad maxima is observed in the region where HCl vapor absorbs. The maxima have been interpreted as arising from a vibrational transition where the rotational angular momentum can increase by one quantum, decrease by one quantum, or remain the same. In the gas phase only the first two kinds of transitions are allowed. The third type of transition is expected when an unsymmetrical electrostatic field, such as that existing locally in the liquid, is present. In this case the major contribution to the field arises indirectly from the HCl dipole which induces a dipole in the neighboring polarizable xenon. This reaction field can act back on the HCl dipole. The field is unsymmetrical because of the defect structure of the liquid state. When there is high symmetry, as in the case of HCl in solid xenon (2S), the perturbed spectrum does not occur ... 

P. D. Dacre. Pair polarizabilities of the heavy inert gases II. SCF calculations of the pair polarizabilities of krypton and xenon. Molec. Phys., 47 193-208 (1982). 

Atom-Atom Interactions. - The methods applied, usually to interactions in the inert gases, are a natural extension of diatomic molecule calculations. From the interaction potentials observable quantities, especially the virial coefficients can be calculated. Maroulis et al.31 have applied the ab initio finite field method to calculate the interaction polarizability of two xenon atoms. A sequence of new basis sets for Xe, especially designed for interaction studies have been employed. It has been verified that values obtained from a standard DFT method are qualitatively correct in describing the interaction polarizability curves. Haskopoulos et al.32 have applied similar methods to calculate the interaction polarizability of the Kr-Xe pair. The second virial coefficients of neon gas have been computed by Hattig et al.,33 using an accurate CCSD(T) potential for the Ne-Ne van der Waals potential and interaction-induced electric dipole polarizabilities and hyperpolarizabilities also obtained by CCSD calculations. The refractivity, electric-field induced SHG coefficients and the virial coefficients were evaluated. The authors claim that the results are expected to be more reliable than current experimental data. 

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. 

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