Depolarized light scattering near the gas-liquid critical point

Publisher Website
Google Scholar
Abstract
We consider a new mechanism for the depolarization of light by simple fluids that arises only in the gas‐liquid critical region. It is shown that the contributions to the integrated scattering intensity can be separated into two distinct kinds: single scatterings off anisotropic clusters of interacting atoms and successive single scatterings off undistorted particles separated by macroscopic distances. Under almost all sample conditions the depolarized spectrum is determined wholly by the former, collision induced effects characterized by the short range, many body fluid structure. Close to the critical point, however, the true double scattering events become dominant and reflect entirely new dependences on wavelength, temperature, and sample size. In the particular case of xenon, we predict — for cell dimensions on the order of a few millimeters and long range correlation lengths (ξ) less than a few hundred angstroms — that the depolarization ratio should increase roughly as ξ2. We also predict a small but observable angle dependence in the integrated depolarized scattering intensity, and we discuss the ``iterated'' (``reducible'') nature of the contributions from three‐ and four‐body structural correlations.