Coherent Rayleigh scattering

The spectrum of coherent scattering induced by electrostriction in gases ha s been analyzed in the previously unexplored, free-molecule limit by solvin g Boltzmann's equation with a periodic force due to the optical fields. Cal culated and measured spectra of several gases at rarefied conditions are ne arly Gaussian with widths approximately 10% wider than the spontaneous Rayl eigh widths. Our results are the first spectrally resolved measurements of coherent Rayleigh scattering in the free-molecule limit, where the hydrodyn amic analysis of stimulated Rayleigh-Brillouin scattering does not apply.