Polarimetric neutron spin echo

Neutron spin echo INSE) spectroscopy inherently involves polarization analysis features. Thus, the very principle of paramagnetic NSE used for the study of magnetically isotropic systems is based on the vector properties of the neutron polarization change in the scattering, which implies that the incoming and outgoing neutron spin directions are not parallel. Another, conventional polarization analysis feature is the opposite sign of the NSE signal for nuclear and nuclear-spin incoherent scattering, or the signal parallel and perpendicular magnetic fluctuations in the presence of a strong magnetizing field. In these cases the measured NSE spectra are the algebraic sums of two components. In its actual form, however, NSE does not allow one to investigate spin-flip and non-spin-Rip scattering channels independently from each other. At the expense of rather moderate loss of signal it is, however, possible to generalize the NSE technique for the study of a given channel of spin-dependent scattering processes in the most general sense of neutron polarimetry. This means to perform inelastic NSE analysis on the partial scattering cross-section corresponding to the transition from any incoming spin direction P to any outgoing spin direction P'. A method of combining NSE with neutron polarimetry will be described together with a simple example of experimental realization. (C) 2001 Elsevier Science B.V. All rights reserved