Effect of multiple scattering on SANS spectra from bicontinuous microemulsions.

Small-angle neutron scattering is a powerful tool for investigating the microstructure of self-assembled systems. The domain length, d, and the correlation length, xi, are two measures of bicontinuous microemulsions that are often determined from coherent SANS spectra. Some microemulsions scatter strongly, however, so measured spectra can contain multiple coherent scattering, and neglect of that multiple scattering can lead to incorrect values of d and xi. In addition, multiple scattering can give rise to artifacts in the spectra, most notably an apparent scattering peak at twice the value of the scattering vector of the main peak. Here, changes in the SANS spectra from strongly scattering microemulsions and the parameters derived from them are reported as a function of relative scattering probability by varying both sample thickness and scattering contrast. A linear extrapolation of the results to zero scattering probability yields good estimates for the microstructural parameters, and the numerical procedure of Schelten and Schmatz is used to calculate the specific effects of multiple scattering on typical bicontinuous microemulsion scattering spectra.