The resolution function in neutron spin-echo spectroscopy with three-axis spectrometers

Abstract

A resolution function for inelastic neutron spin-echo spectroscopy on a three-axis spectrometer is derived. Inelastic dispersive excitations where the tilted field technique applies are being considered. Using a Gaussian approximation of the transmission function of the three-axis spectrometer and a second-order expansion of the total Larmor phase, the instrumental resolution function of an idealized spin-echo instrument is obtained. Furthermore, the resolution function is extended to include the effects of sample properties, such as mosaicity, spread in lattice spacings and the curvature of the four-dimensional dispersion surface in a line-width measurement.