Editing Neutron scattering (section)

==Inelastic neutron scattering==
[[Image:inelastic-neutron-scattering-basics.png|thumb|300px|Generic layout of an inelastic neutron scattering experiment]]
[[File:Inelastic Neutron Scattering.webm|thumb|Inelastic Neutron Scattering]]
'''Inelastic neutron scattering''' is an experimental technique commonly used in [[condensed matter physics|condensed matter research]] to study atomic and molecular motion as well as magnetic and crystal field excitations.<ref>G L Squires ''Introduction to the Theory of Thermal Neutron Scattering'' Dover 1997 (reprint?)</ref><ref name=PhD-474621>{{cite thesis|degree=DPhil|publisher=University of Oxford|url=http://solo.bodleian.ox.ac.uk/permalink/f/89vilt/oxfaleph019872832|authorlink=Andrew D. Taylor|title=Inelastic Neutron Scattering by Chemical Rate Processes|first= Andrew Dawson|last=Taylor|date=1976|id={{EThOS|uk.bl.ethos.474621}}|website=ox.ac.uk|oclc=500576530}}</ref> It distinguishes itself from other neutron scattering techniques by resolving the change in kinetic energy that occurs when the collision between neutrons and the sample is an inelastic one. Results are generally communicated as the [[dynamic structure factor]] (also called inelastic scattering law) <math>S(\mathbf{Q},\omega)</math>, sometimes also as the dynamic susceptibility <math> \chi^{\prime \prime}(\mathbf{Q},\omega)</math> where the scattering vector <math>\mathbf{Q}</math> is the difference between incoming and outgoing [[wave vector]], and ''<math>\hbar \omega</math>'' is the energy change experienced by the sample (negative that of the scattered neutron). When results are plotted as function of <math>\omega</math>, they can often be interpreted in the same way as spectra obtained by conventional [[spectroscopy|spectroscopic]] techniques; insofar as inelastic neutron scattering can be seen as a special spectroscopy.

Inelastic scattering experiments normally require a [[monochromatization]] of the incident or outgoing beam and an energy analysis of the scattered neutrons. This can be done either through time-of-flight techniques ([[neutron time-of-flight scattering]]) or through [[Bragg reflection]] from single crystals ([[neutron triple-axis spectroscopy]], [[neutron backscattering]]). Monochromatization is not needed in echo techniques ([[neutron spin echo]], [[neutron resonance spin echo]]), which use the quantum mechanical [[phase (waves)|phase]] of the neutrons in addition to their amplitudes.{{cn|date=February 2019}}