Perturber dependence of the collision-induced light scattering by SF₆and CF₄

Abstract

The two-body collision-induced light scattering spectra of pure SF 6 and CF4 and of their mixtures with inert gases have been measured at 295 K. The data were compared with calculations of the spectral profiles. These comparisons enabled: (i) the testing of a scaling law for the pair polarizability anisotropy responsible for the purely translational scattering; (ii) the determination of refined values for the magnitudes of the dipole-octopole polarizability ((10-7 + 2) x 10 -s~ m 5) of SF 6 and of the dipole-quadrupole ((2.5 + 0.3) x 10-4~ 4) and dipole--octopole ((2.5 + 0.3) x 10-S~ 5) polarizabilities of CF4; and (iii) the assessment of the suitability of available intermolecular potentials for describing the interaction leading to the scattering, particularly for SF6-SF 6 , SF6-Kr and CF4-Ar.

Anisotropic collision-induced Raman scattering by the Kr:Xe gas mixture

“…This is because the atoms of a gas, unlike the atoms in a molecule, interact through van der Waals forces ͑as opposed to the chemical binding forces͒, so atomic pairs are systems far more delicate than ordinary diatomic molecules. Although some gas mixtures involving a monoatomic gas have been studied previously in CIS ͓for instance, SF 6 and CF 4 have been studied in mixtures with Ar, Kr, and Ne; 14 CO 2 has been studied in mixture with Ar ͑Ref. 15͔͒, only little is known about CIS in a mixture of two monoatomic gases.…”

An Approximate Empirical Intermolecular Potential for CF4–Ar

“…There is another component due to induced rotational scattering [7]. Its shape is largely determined by the total angular momentum quantum number selection rules and its intensity depends on the magnitude of the dipolequadrupole and dipole-octopole polarizabilities of CF 4 .…”

“…Thus, it is useful to give some details of the profile calculation, although they are available elsewhere [7]. At moderate densities, the CILS spectrum is determined by binary interactions.…”

“…It consists of two components, one due to purely translational scattering and the other to induced rotational Raman scattering. The pair polarizability giving rise to the translational scattering has been modeled, in the case of mixture [7,18], as…”

“…The experimental data for the five properties of the CF 4 -Ar are given in [3,[5][6][7][8]. We should note, however, that the data for the pressure virial coefficient is available only for a small temperature range, i.e.…”