Motional diminishing of optical activity: a novel method for studying   molecular dynamics in liquids and plastic crystals
  Molecular dynamics calculations and optical spectroscopy measurements of weakly active infrared modes are reported. The results are qualitatively understood in terms of the "motional diminishing" of IR lines, a process analogous to the motional narrowing of a nuclear magnetic resonance (NMR) signal. In molecular solids or liquids where the appropriate intramolecular resonances are observable, motional diminishing can be used to study the fluctuations of the intermolecular interactions having time scales of 1psec to 100psec. 
Michael C. Martin and Laszlo Mihaly (Dept. of Physics, SUNY at Stony   Brook)