International
Tables for Crystallography Volume H Powder diffraction Edited by C. J. Gilmore, J. A. Kaduk and H. Schenk © International Union of Crystallography 2018 |
International Tables for Crystallography (2018). Vol. H, ch. 2.3, p. 69
Section 2.3.2.4. Neutron attenuation^{a}School of Engineering, University of Newcastle, Callaghan, NSW 2308, Australia |
Neutron beams are attenuated by coherent scattering, incoherent scattering and true absorption. The cross sections for all these processes are included in the tables cited above. For powder diffraction, the coherent scattering is usually small because it takes place only in that small fraction of crystallites correctly oriented for Bragg reflection; the other processes, however, take place throughout the sample.
If a particular scattering entity i with scattering cross sections (σ_{i})_{inc} and (σ_{i})_{abs} is present at a number density N_{i}, then the contribution it makes to the linear attenuation coefficient μ is . If the mass is M_{i}, then the density is simply , so we have the means to evaluate the mass absorption coefficient . The calculation of absorption for elements, compounds and mixtures commonly proceeds by the manipulation of mass absorption coefficients, in the same manner as is employed for X-rays (see Section 2.4.2 in Kisi & Howard, 2008).
References
Kisi, E. H. & Howard, C. J. (2008). Applications of Neutron Powder Diffraction. Oxford University Press.Google Scholar