Space-time view of neutron spin echo, correlation functions and phonon focusing

We discuss first inelastic scattering without dispersion in neutron spin echo (NSE) spectroscopy in terms of the conventional view using classical Larmor precession. A strict quantum mechanical treatment follows, which considers the interaction of the neutron with the field and the scattering process quantum mechanically. The spacetime view of NSE is presented in a semi-classical (ray-tracing) picture. An introductory treatment of the `phonon focusing' technique with inclined precession field boundaries is given in (Q,w)-space and the space-time view is applied to the more general case of inelastic scattering with dispersion present.