Scattering of neutrons

Thru 1967, emphasis was given to the use of neutrons as the bombarding source of radiation. Almost all possible neutron reactions were considered including moderation of fast neutrons by hydrogen in the expl, thermal capture reactions, elastic and inelastic scattering of neutrons and neutron activation reactions. These neutron reactions are listed as follows ... 

The scattering of neutrons by any molecular system can be elastic or inelastic, coherent or incoherent. The elastic coherent scattering of a labeled polymer in a background matrix can be extracted from the data in a properly designed experiment. 

The most important experiment of this type is thermal neutron scattering A complete determination of the differential scattering cross section for the scattering of neutrons from liquids completely determines the Van Hove scattering function.18 This function is related through a space-time Fourier transform to the autocorrelation function of the number density at two... 

M. Blume, Symposium of Inelastic Scattering of Neutrons by Condensed Systems, Brookhaven National Laboratory, September 1965. 

If we find the structural factor from some independent experimental data, say, from those concerning the scattering of neutrons, relation (3.25) will enable us to find the loss function also. Since the structural factor is determined by the density-density electron correlation function, relation (3.25) implies that the excitation of plasmon oscillations is determined by the correlation in electron motion. 

Kappula, H., and Glaser, W. 1972. In Inelastic Scattering of Neutrons in Solids and Liquids. Vienna IAEA, p. 841. 

The scattering of neutrons, ions, or electrons results in changes in both the energy and momentum of these particles. Structural information is obtained from the measurement of these changes. 

Inelastic scattering of neutrons yields neutron scattering spectra that measure the vibrational energy levels of the material under study. For example, the chemisorption of water on Raney nickel was shown by inelastic scattering both to produce hydroxyl groups and to chemisorb water molecules on the surface at less than monolayer coverages. 

Dean P (1967) Atomic vibration in solids. J Inst Math Appl 3 98—165 De Gennes PG (1967) Quasi-elastic scattering of neutrons by dilute polymer solutions I. Free-draining limit. Physics 3(1) 37—45... 

The classical idea of molecular structure gained its entry into quantum theory on the basis of the Born Oppenheimer approximation, albeit not as a non-classical concept. The B-0 assumption makes a clear distinction between the mechanical behaviour of atomic nuclei and electrons, which obeys quantum laws only for the latter. Any attempt to retrieve chemical structure quantum-mechanically must therefore be based on the analysis of electron charge density. This procedure is supported by crystallographic theory and the assumption that X-rays are scattered on electrons. Extended to the scattering of neutrons it can finally be shown that the atomic distribution in crystalline solids is identical with molecular structures defined by X-ray diffraction. 

Hoinkis E. Small-angle scattering of neutrons and x-rays from carbons and graphites. In Thrower PA, ed. Chemistry and Physics of Carbon, vol. 25, New York Marcel Dekker. 1997 71-241. 

Two of the more direct techniques used in the study of lattice dynamics of crystals have been the scattering of neutrons and of x-rays from crystals. In addition, the phonon vibrational spectrum can be inferred from careful analysis of measurements of specific heat and elastic constants. In studies of Bragg reflection of x-rays (which involves no loss of energy to the lattice), it was found that temperature has a strong influence on the intensity of the reflected lines. The intensity of the scattered x-rays as a function of temperature can be expressed by I (T) = IQ e"2Tr(r) where 2W(T) is called the Debye-Waller factor. Similarly in the Mossbauer effect, gamma rays are emitted or absorbed without loss of energy and without change in the quantum state of the lattice by... 

Fig. 2.2-Ic illustrates a similar process, the inelastic scattering of neutrons. Irradiating molecules with mono-energetic neutrons produce scattered neutrons according to an energy balance equivalent to Eq. 2.2-1. While Raman scattering as well as infrared absorption of symmetric molecules obeys strict selection rules, which allow or forbid the activity of certain vibrations in these spectra, inelastic scattering of neutrons is not subject to such rules. It is not usually applied in analytical chemistry, but it is used to study lattice vibrations of crystals in solid-state physics and dynamics of liquids.

The general cross section for the scattering of neutrons by magnetic interactions, derived from the master formula [Eq. (3.4)] and the interaction potential between a neutron and an electron with spin and momentum is derived by Marshall and... 

Small-Angle Scattering of Neutrons and X-rays from Carbons and Graphites, Ernst Hoinkis... 

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