Elucidation of SESANS correlation functions through model

Abstract

Several single-modal Debye correlation functions are closely examined to elucidate the behavior of their corresponding SESANS (Spin Echo Small Angle Neutron Scattering) correlation functions. We ¯nd that the upper bound of a Debye correlation function and of its SESANS correlation func- tion is identical. For discrete Debye correlation functions, the peak of SESANS correlation function emerges at their ¯rst discrete point, whereas for continuous Debye correlation functions with greater width, the peak position shifts to a greater value. In both cases, the intensity and shape of the peak of the SESANS correlation function are determined by the width of the normalized Debye correlation functions. In the application, we mimic the intramolecular and intermolecular Debye correlation functions of liquids composed of interacting particles by using the simple models to elucidate their competition in the SESANS correlation function. Our calculations show that the position of the ¯rst minimum of SESANS correlation function shifts to a smaller value as inter- molecular attraction or correlation is enhanced. The minimum value can be positive or negative, and the positive values are observed for the cases equivalent to stronger intermolecular attraction, consistent with literature results based on more sophisticated liquid state theory and simulations.