Abstract
The intensity of neutron inelastic scattering by phonons is considered, using the symmetry properties, by group theoretical methods (the extension to scattering by magnons is briefly discussed). Under some circumstances there are selection rules forbidding scattering at particular K values and, by examining the phonons at a series of points K = k+G for different reciProc.al lattice points G, it is often possible to make a definite symmetry identification of the various branches. It is hoped that the results will be of use in the interpretation of experimental data in more complicated crystals than have so far been studied. The fluorite and cuprite structures are considered as examples which might soon be profitably investigated. Standard projection operator techniques are employed.