Neutron back scattering spectroscopy

The back scattering spectrometer enables access to fast dynamic processes on a structural length (0.1-1nm) below the SANS range (SPHERES at FRMII and partly at BASIS in Oak Ridge). Back scattering spectroscopy observes dynamic processes on a time scale between around 10ps and ns. However, unlike the NSE in terms of the range of energy distribution of the scattered neutrons, the resolution is typically in the area of µeV (SPHERES: 0.7µeV, BASIS: 4µeV). Here, mostly the dynamics of the self-correlation of protons in the sample are measured, in the form of “incoherent” scattering, which helps considerably with detecting the signal.

As well as proton diffusion (e.g. in proton conducting or hydrogen storage materials), this signal gives us information about the mobility of molecular groups to which protons belong, and also for example, about the segment mobility of polymers or amino acids or water in proteins. Back scattering bridges the gap between NSE and time-of-flight spectrometry (TOF).