Diffuse Scattering Spectrometer
D7 has been dismantled. The new permanently-polarized diffuse scattering spectrometer D007 will deliver its first neutrons in 2024.
Separation of coherent and incoherent scattering
Protonated hydrogen has a very large nuclear-spin incoherent cross-section for neutrons. This contribution is often regarded as sample-dependent 'background', masking the coherent scattering that gives information on the structure.
The nuclear-spin incoherent scattering is polarization-dependent, and polarization analysis is sometimes used to separate and discard this contribution. The incoherent can, however, contain useful information for the dynamics of a material. The incoherent spectrum gives information on the motion of individual hydrogen atoms and hydrogenated molecules, while the coherent spectrum gives information on collective motion.
In using its time-of-flight option in conjunction with polarization analysis, D7 can separate the incoherent and coherent scattering to give unambiguous information on the structure, the dynamics of individual molecules, and on the collective dynamics in a sample.
The example here shows measurements on pyridinium-based ionic liquids. These materials are basically salts that have a melting temperature somewhere below 100° Celsius. They have multiple possible uses, particularly in electrochemistry.
Ref: T. Burankova, R. Hempelmann, A. Wildes and J. P. Embs, J. Phys. Chem. B, 118 14452 (2014)