NRSE

NRSE, short for Neutron Resonance Spin Echo, is a neutron scattering technique that applies spin-echo concepts to measure very small energy transfers in materials. By encoding the dynamics of a sample into the phase evolution of polarized neutrons, NRSE provides high energy resolution over time scales ranging from picoseconds to nanoseconds.

Principle: A beam of polarized neutrons traverses regions of magnetic field interleaved with resonant radiofrequency spin flippers. The spin precession in the magnetic fields encodes an energy difference into a controllable phase. Two RF flippers and carefully arranged field regions create an effective spin-echo condition, so that neutrons which experience no net energy change accumulate a refocused spin phase. The detected polarization as a function of the adjustable phase or time parameter yields information about the sample’s dynamics. The measured signal is related to the intermediate scattering function F(Q, t) and, via Fourier relations, to the dynamic structure factor S(Q, ω).

Variants and applications: Longitudinal NRSE (LNRSE) and Transverse NRSE (TNRSE) denote different geometries of the static magnetic fields, affecting sensitivity and the accessible ranges of momentum transfer Q and energy transfer ω. NRSE can offer compact instrumentation and can mitigate certain depolarization effects compared with conventional Neutron Spin Echo (NSE). It is used to study slow dynamics in liquids, polymers, magnetic materials, and soft matter, as well as diffusion and molecular motions in complex systems.

Disambiguation and context: In physics literature, NRSE most commonly refers to Neutron Resonance Spin Echo. See also neutron spin echo, NSE, and polarized neutron scattering.