Mean square displacement from self-distribution function evaluation by elastic incoherent neutron scattering

The determination of the different contributions to the mean square displacement (MSD) associated with different relaxation mechanisms together with their time and thermal behaviour is performed by evaluating the self-distribution function derived by Elastic Incoherent Neutron Scattering (EINS). The analysis of the standard approach for MSD determination leads to an operational recipe that highlights the connection with the self-distribution function. The approach is tested on EINS data collected by the backscattering spectrometer IN13 (ILL, Grenoble) on a model system such as PolyEthylene Glycol with mean molecular weight Mw = 400 (PEG 400).