Three-body depolarized interaction-induced light-scattering spectrum of neon

We report the results of a depolarized interaction-induced light-scattering (DILS) experiment on gaseous neon at room temperature, from which the two- and three-body induced spectra have been extracted. The two-body spectrum is in excellent agreement (in absolute units) with a previous determination by Frommhold and Proffitt [Phys. Rev. A 21, 1249 (1980)], while the three-body spectrum is a new result. The comparison of the three-body experimental spectral moments with a calculation performed within the pairwise additivity approximation shows a discrepancy which is of opposite sign to that observed in krypton. The calculations have been carried out including the first-order correction of the Wigner-Kirkwood expansion in order to take into account quantum effects. We suggest that the occurence of irreducible three-body effects may be due to more than one microscopic mechanism and these can be usefully investigated by means of DILS spectroscopy.