Interpretation of correlation length by small-angle X-ray scattering experiments on fluids near critical point

Abstract

Small-angle X-ray scattering from fluids near the critical point, such as CHF 3, CO 2, Xe, and H 2O, was analyzed using an intensity distribution function of fluctuating structures, D( R), in order to investigate the inhomogeneity in these fluids. It was found that the function D( R) ∝ 1/( R 4 + L 4) could provide a good approximation of the intensity distribution functions of the fluctuating structures in the fluids. The Ornstein–Zernike correlation length ( ξ) was found to be related to the half width at half maximum ( L) of D( R): ξ was approximately 5/18 of L.