Elastic and inelastic scattering from NH4Br measured by mössbauer γ-ray diffraction

Abstract

The thermal diffuse scattering from a single crystal of NH4Br is investigated in the disordered high temperature range 293 K ≦ T ≦ 410 K up to the CsClNaCl structural phase transition. The diffraction of γ‐rays from a 2757Co Mössbauer source is utilized to discriminate between elastic and inelastic scattering events with an energy resolution dE = 28 neV. Two experimental procedures are proposed. For comparison with the experiments the inelastic cross‐section is evaluated from a lattice dynamical calculation in the long wavelength one‐phonon approximation. Enhanced inelastic intensities near Tc are observed.

Temperature Dependent Frequency Shifts in the Resonance Absorption and Resonance Fluorescence Scattering of Mössbauer γ‐Quanta

“…Since we have been interested in our laboratory in the application of Mossbauer y-quanta in diffraction experiments, the role of relativistic effects in such experiments should be known for a refined interpretation. Among these diffraction experiments we mention the temperature dependent elastic and inelastic scattering from the molecular crystal NH,Br [6], the logarithmically divergent thermal diffuse scattering near the upper phase transition of KCN [7], the y-Brillouin scattering from an oscillating quartz crystal [8], and the interference between the nuclear resonance scattering and the electronic Rayleigh scattering from the iron containing compound Na,Fe(CN),NO . 2 H,O [9].…”

Temperature Dependent Energy Shifts in the Resonance Absorption and Resonance Fluorescence Scattering of Mössbauer γ‐Quanta in FeS2

“…The Mossbauer y-ray diffraction method we use has been explained in previous papers 113, 141; therefore we only describe shortly the modifications in our present set-up. A 5.5 MBq s7C0 source in a Rh matrix was mounted on a Mossbauer transducer.…”

Moessbauer spectroscopy

“…The thermal diffuse scattering from a single crystal of NH4Br was studied by Martin et al (95) in the temperature range of 293-410 K. By using diffraction of 7 rays, they were able to discriminate between the elastic and inelastic scattering events with an energy resolution of 28 neV. In another diffraction experiment single crystals of sodium nitroprusside are used.…”