Today we measured our first inelastic neutron scattering spectrum on our PELICAN time-of-flight spectrometer, from a sheet of polyethylene using an incident neutron energy of 3.74 meV.
We have subsequently obtained the quasi-elastic spectrum from water at room temperature with the same instrument configuration.
The elastic line is at 0.0 meV and the other scattering in both neutron energy loss and neutron energy gain, on either side of the elastic signal is essentially from the vibrational density of states in the sample.
The self-diffusion constant extracted from the quasielastic width of these raw data is 1.9 x 10-9 m2s-1, which is in very good agreement with the literature value of 1.85 x 10-9 m2s-1 (Singwi and Sjolander, Phys. Rev. 119, (1960)).
