Refraction inert gases

Since the index of refraction in an atomic inert gas at a frequency far from an absorption transition is very close to 1.00, the phase matching scheme for the frequency tripling process,... 

When kept under inert gas at low temperatures the product remains unchanged for at least 24 h if air is admitted, however, the refractive index soon rises, and attempts to distill the compound result in decomposition and formation of high-boiling material. 

These numbers are related in the right sense to the a-values of the inert gases. This connection can be traced still further by considering the a-values of other (multiple-valued) ions of inert gas type, which may be determined partly from the Rydberg corrections of spectra of the ionised element (spark spectra), partly from the refractive indices of solid salts, (ionic lattice). In this way further support is obtained for the view that the Rydberg correction of the terms of the outer orbits in the spectra under consideration is due to the... 

For the isotropic inert gas spectrathe situation is rather less well settled. As anticipated above, from the vanishing first order DID term, the spectra are very weak and difficult to observe, and a reliable theoretical basis for the interpretation of the data is lacking. As yet no model for the isotropic part of the polarizability of an atomic pair has emerged which can simultaneously account for the light scattering spectra and the refractive index (or dielectric) virial data and which is consistent with ab initio calculations. However there has been a good deal of recent activity on this topic ). 

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. 

The polarity of isolated solvent molecules is given by their dipole moments p as measured in the gas phase or in inert solvents. The polarizability of solvent molecules a is obtained from measurements of the refractive index n and the density p, yielding the molar refraction R, given the relative molar mass M (equation 6) ... 

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