High-frequency interaction-induced rototranslational scattering from gaseous nitrogen.

Abstract

${\mathrm{N}}_{2}$ gas rototranslational scattering is studied at high frequency up to 700 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ theoretically and experimentally for several temperatures and from low densities up to 170 amagat. Our theoretical calculations take into account multipole contributions from the mean value and anisotropy of the dipole-dipole polarizability tensor a\ensuremath{\rightarrow} and two independent components of the dipole-octopole polarizability tensor E\ensuremath{\rightarrow}. The E\ensuremath{\rightarrow} tensor is found to give the most important contribution at high frequency. The comparison of the experimental and theoretical spectra allows us to estimate at \ensuremath{\Vert}E\ifmmode \tilde{}\else \~{}\fi{} $_{0}^{(4)}\mathrm{\ensuremath{\Vert}}$=4.6 \AA{} $^{5}$ the absolute value of the experimental (\ensuremath{\lambda}=514.5 nm) dynamic irreducible spherical component of the dipole-octopole polarizability tensor of ${\mathrm{N}}_{2}$. When using this value, good agreement is obtained between the theoretical and experimental spectra at room temperature (294 K) and low temperature (150 K).