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Encyclopedia > Neutron scattering

The term "Neutron Scattering" encompasses all scientific techniques whereby neutrons are used as a scientific probe.

For several good reasons, neutrons provide an ideal tool for the study of all forms of condensed matter. Firstly, they are readily produced at a moderated nuclear reactor and spallation source with wavelengths that are comparable to the atomic spacing in solids and liquids, and kinetic energies that are comparable to those of dynamic processes in materials. This causes pronounced interference and energy transfer effects in scattering experiments. Unlike an x-ray photon with a similar wavelength, which interacts with the electron cloud surrounding the nucleus, neutrons interact with the nucleus itself. Because the neutron is an electrically neutral particle, it is deeply penetrating, and is therefore more able to probe the bulk material. Consequently, it enables the use of a wide range of sample environments that are difficult to use with synchrotron x-ray sources. Moreover, the nucleus provides a very short range, isotropic potential varying randomly from isotope to isotope, making it possible to tune the nuclear scattering contrast to suit the experiment. A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate (as opposed to a nuclear explosion, where the chain reaction occurs in a split second). ... In nuclear physics, spallation is the process in which a heavy nucleus emits a large number of nucleons as a result of being hit by a high-energy proton, thus greatly reducing its atomic weight. ...

The neutron has an additional advantage over the x-ray photon in the study of condensed matter. It readily interacts with internal magnetic fields in the sample. Infact, the strength of the magnetic scattering signal is often very similar to that of the nuclear scattering signal in many materials, which allows the simultaneous exploration of both nuclear and magnetic structure.

See also Neutron diffraction. In quantum physics, neutrons are particles that can occur as building blocks of atomic nuclei. ...

  Results from FactBites:
Neutron properties (869 words)
Neutron scattering gives detailed information about the microscopic behavior of condensed matter, playing a major role in shaping the experimental and theoretical understanding of materials ranging from magnetism and superconductivity to chemical surfaces and interfaces.
Neutrons are spin-1/2 particles and therefore have a magnetic moment that can couple directly to spatial and temporal variations of the magnetisation of materials on an atomic scale.
The cross-sections for magnetic scattering and scattering from the chemical structure are fortunately of the same magnitude, permitting the simultaneous measurement of the magnetic and chemical behaviour of materials.
Neutron Scattering (600 words)
Neutrons, produced either as a product of nuclear fission in a reactor, or by a spallation process, have energies which depend on the temperature of the moderator used to reduce their energies.
Neutrons also possess wavelengths which are ideally suited to allow measurement of structural information over a huge range, covering the wavefunction of hydrogen to structural morphology of macromolecules.
Neutrons also possess a spin and consequently a magnetic moment which can interact with any unpaired electrons in the sample, although this is not widely exploited by the polymer community.
  More results at FactBites »



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