A resolution model for mode multiplets probed with neutron resonance spin-echo spectroscopy

A resolution model, which takes into account a violation of the spin-echo conditions for inelastic scattering as it is appropriate for high resolution spin-echo measurements of mode multiplets, is experimentally tested. Phase-sensitive measurements were performed while a dispersion surface is moved through the resolution ellipsoid of a triple-axis background spectrometer. The results are found to be in agreement with the model predictions. A tunable, artificially split dispersion was realized with a double crystal setup mounted on a piezoelectric device allowing for rotation and tilt of the first crystal, while the second one was rigidly fixed. Elastic measurements with the instrument configured in Larmor diffraction geometry were used to probe the crystal orientation with high sensitivity. First inelastic measurements are in agreement with a simplified model indicating persistence of the echo modulation over the entire spin-echo time range probed by the experiment.