Accessing self-diffusion on ns time and nm length scales with minute kinetic resolution
What is it about?
We have developed a new analysis framework allowing to access the diffusion coefficient from quasi elastic neutron backscattering fixed window scans (FWS). The analysis pipeline is applicable to colloidal suspensions as well as to hydrated powders, where the elastic incoherent scattering structure factor can be extracted.
Why is it important?
Quasielastic neutron backscattering offers a unique access to the nanosecond short-time diffusive properties including simultaneously information on the nanometer length scale. Due to the limited flux, classical full QENS spectra are limited to relatively high concentrations (> 50 mg/ml). Since the FWS offer a significantly higher neutron flux at the sample position, the investigation of kinetic samples and lower concentrated samples is now feasible. However, due to the reduced number of energy transfers investigated, standard data analysis frameworks fail. The new framework for FWS with an acquisition time in the order of 10 minutes offers a quantitative agreement to the classical QENS analysis of full QENS data acquired during several hours.