Page 65 - Neutrons for Sciences and Society

Chapter 3 - Why invest so much money in a source of neutrons?
necessarily conserved. Hence scans changing neutron energy transfer or momentum transfer will show peaks in intensity of scattered neutrons which correspond exactly to these values for the created (or emitted) phonons.
3.2 Neutrons and Condensed Matter
The vast majority of applications of neutrons lie in this area. They make use of the following properties. From quantum mechanics we know that all elementary particles have at the same time
both wave like and particle properties. Thermal neutrons have wavelengths of the order of 1 Ångström51. Cold neutrons have wavelengths of the order of 5 Å. These neutrons have energies comparable to phonon energies E. These two characteristics together of neutrons make them especially well adapted to study simultaneously structure and internal motions of these structures. There are two fields where this is applied : diffraction, which employs the wave-like nature of neutrons, to determine average atomic positions (structure), and inelastic scattering, which depends essentially on the corpuscular nature of neutrons, to study dynamics.
51 One centimetre is equal to 100 million Ångström (Å).
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