Abstract
A detailed calculation is presented of the resolution properties of a three-axis neutron spectrometer equipped with a neutron spin-echo device. The calculation shows that the Fourier transform of the spectral density of an elementary excitation may be measured with a resolution which is substantially better than that available with a conventional three-axis spectrometer. In contrast to conventional spectrometers the spin-echo technique allows focusing of both longitudinal and transverse phonon modes.