Density noble gases

The constants e and o have been measured for the low-density noble gases. It is possible to estimate some properties of solid gases using only these values and the potential (15.11) [7]. 

Mavri, J., Berendsen, H.J.C. Dynamical simulation of a quantum harmonic oscillator in a noble-gas bath by density matrix evolution. Phys. Rev. E 50 (1994) 198-204. 

The blue satellite peak associated with resonance line of rubidium (Rb) saturated with a noble gas was closely examined by Lepoint-Mullie et al. [10] They observed SL from RbCl aqueous solution and from a 1-octanol solution of rubidium 1-octanolate saturated with argon or krypton at a frequency of 20 kHz. Figure 13.4 shows the comparison of the SL spectra of the satellite peaks of Rb-Ar and Rb-Kr in water (Fig. 13.4b) and in 1-octanol (Fig. 13.4c) with the gas-phase fluorescence spectra (Fig. 13.4a) associated with the B —> X transition of Rb-Ar and Rb-Kr van der Waals molecules. The positions of the blue satellite peaks obtained in SL experiments, as indicated by arrows, exactly correspond to those obtained in the gas-phase fluorescence experiments. Lepoint-Mullie et al. attributed the blue satellites to B — X transitions of alkali-metal/rare-gas van der Waals species, which suggested that alkali-metal atom emission occurs inside cavitating bubbles. They estimated the intracavity relative density to be 18 from the shift of the resonance line by a similar procedure to that adopted by Sehgal et al. [14],... 

He found that both the melting curves (Figure 2.1a) and the densities (Figure 2.1b) for xenon and krypton are well above the estimated temperature and density of the lower mantle. One might then suppose that Xe and Kr are in solid form in the lower mantle. If this is indeed the case, implications on noble gas degassing from the mantle and hence on the evolution of the atmosphere would be far-reaching (cf. Section 6.9). However, the formation of solid Xe or Kr seems to be unlikely because of its... 

Mechanical shock applied in ambient noble gas atmospere also emplaces substantial amount of noble gases into target material. Wiens and Pepin (1988) studied the effects of mechanical shock (20-60 GPa) applied to rock specimens (basalt disk and powder 63-125 pm in size) in ambient air. They found that emplacement efficiencies (number densities in shocked samples/number densities in ambient gases)... 

It obviously follows that the noble gas rule is an empirical and formal one and that the electron density effectively concentrated along a polyhedral edge must be less than required by the rule. Nevertheless, deviations are quantitatively small and the rule is often a useful formalism. 

In order to describe the cohesion in the same terms as was done for metals and noble gas crystals, electron density is proposed to accumulate in the vacant interstitial octahedral sites and the remaining tetrahedral sites. This distribution is shown for two CC4 tetrahedral units in Figure 5.17. The central carbon in the outlined tetrahedron is surrounded by an octahedron (in stippled outline) of interstitials defined by the set of vacant tetrahedral sites. 

When a nonpolar molecule (or a noble gas atom) encounters an ion, its electron density is temporarily distorted resulting in an induced dipole that will be attracted to the ion. Intermolecular attractions due to induced dipoles in a nonpolar molecule are known as London forces or Van der Waals interactions. These are very weak intermolecular forces. 

For obtaining interaction energies and equilibrium geometries, local density approximation is even less adequate than it is in the case of hydrogen-bonded complexes. The intermolecular distances are too short and the interaction energies are overestimated.113,123,127-129,130,131 The overestimation of the interaction energy in the case of noble-gas dimers by factor three as it is the case for Ar2 or even ten for He2127 makes LDA rather useless for this type of systems. 

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