Anisotropic collision-induced Raman scattering by Ne-Ne: Evidence for a nonsmooth spectral wing

We report the anisotropic collision-induced scattering (CIS) spectrum of two neon atoms at room temperature. The covered spectral range hitherto restricted to 170 cm(-1) is here tripled. Both our measurements and quantum-mechanical calculations obtained on the basis of large-scale ab initio anisotropy representations reveal a well-defined saddle-shaped wing. This peculiar structure is experimental evidence of a binary CIS line shape with an aspect other than a smooth wing in a logarithmic plot. Equally interesting is the fact that this feature has been predicted (though only qualitatively) by the simple semiempirical model long ago reported by Meinander, Tabisz, and Zoppi [J. Chem. Phys. 84, 3005 (1986)], but no emphasis had at that time been placed on the aspect of the wing of the model spectrum probably due to the lack of high-frequency experimental data.