Quasielastic neutron scattering (QENS) designates a limiting case of

inelastic neutron scattering Neutron scattering, the irregular dispersal of free neutrons by matter, can refer to either the naturally occurring physical process itself or to the man-made experimental techniques that use the natural process for investigating materials. Th ...

, characterized by energy transfers being small compared to the incident energy of the scattered particles. In a more strict meaning, it denotes scattering processes where dynamics in the sample (such as diffusive dynamics) lead to a broadening of the incident neutron spectrum, in contrast to, e.g., the scattering from a diffusionless crystal, where the scattered neutron energy spectrum consists of an elastic line (corresponding to no energy transfer with the sample) and a number of well-separated inelastic lines due to the creation or annihilation of

phonon A phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids. In the context of optically trapped objects, the quantized vibration mode can be defined a ...

s with specific energies. The term

quasielastic scattering In physics, quasielastic scattering designates a limiting case of inelastic scattering, characterized by energy transfers being small compared to the incident energy of the scattered particles. The term was originally coined in nuclear physics. I ...

was originally coined in nuclear physics. It was applied to thermal

neutron scattering Neutron scattering, the irregular dispersal of free neutrons by matter, can refer to either the naturally occurring physical process itself or to the man-made experimental techniques that use the natural process for investigating materials. Th ...

since the early 1960s, notably in an article by Leon van Hove and in a highly cited one by Pierre Gilles de Gennes. QENS is typically investigated on high-resolution spectrometers (

neutron backscattering Neutron backscattering is one of several inelastic neutron scattering techniques. Backscattering from monochromator and analyzer crystals is used to achieve an energy resolution on the order of a microelectronvolt (μeV). Neutron backscattering e ...

neutron time-of-flight scattering In neutron time-of-flight scattering, a form of inelastic neutron scattering, the initial position and velocity of a pulse of neutrons are fixed, and their final position and the time after the pulse that the neutrons are detected are measured. By ...

, neutron spin echo). It is used to investigate topics like * solid-state diffusion (e.g. hydrogen in metals) * slow modes in crystals (e.g. methyl group rotation) * relaxation of viscous liquids

Conference Series

Starting in 1992, there is a conference series entitled QENS. Since 2012, it is being held together with the Workshop on Inelastic Neutron Spectrometry (WINS).

Textbooks

* M. Beé, ''Quasielastic Neutron Scattering'', Adam Hilger: Bristol (1988). * R. Hempelmann, ''Quasielastic Neutron Scattering and Solid State Diffusion'', Clarendon Press: Oxford (2000).

References

{{Reflist Neutron scattering