The theory of the neutron Kikuchi effect has been re-examined and an exact formulation in reciprocal space derived. The conditions necessary for its observation have been considered and appropriate data from a lead single crystal have been collected on the triple-axis spectrometer at the HIFAR reactor in the laboratories of the Australian Nuclear Science and Technology Organisation. A series of constant-Q phonon scans across the predicted positions of the Kikuchi lines show reductions in the integrated phonon intensity, which appear to move as expected with changes in the scattered neutron wavevector.

The elastic and inelastic components of y-ray scattering from a non-transforming VaSi single crystal have been measured using a 57CO Mossbauer source and resonant absorber. The system places an upper limit of � 4 x 10 - 8 e V on the possible energy transfer which distinguishes inelastic from elastic scattering. The scattering at the (440) Bragg reflection with q = 0 and q - 0�1 A -1 has been measured as a function of temperature for two orthogonal orientations of the crystal. Anomalous changes in the elastic and inelastic intensities have been observed. It is suggested that these changes are associated respectively with central mode and soft mode aspects of the dynamics of the vanadium atoms.

No abstract

No abstract

No abstract