Neutron Spin Echo Spectroscopy Peter Fouquet
[email protected] Institut Laue-Langevin Grenoble, France Oxford Neutron School 2017 What you are supposed to learn in this tutorial 1. The length and time scales that can be studied using NSE spectroscopy 2. The measurement principle of NSE spectroscopy 3. Discrimination techniques for coherent, incoherent and magnetic dynamics 4. To which scientific problems can I apply NSE spectroscopy? NSE-Tutorial Mind Map Quantum Mechanical Model Resonance Spin-Echo Classical Model Measurement principle “4-point Echo” NSE spectroscopy Instrument Frustrated Components Magnets Bio- molecules Time/Space Map NSE around Surface the globe Diffusion Science Cases Paramagnetic Spin Echo Experiment planning and Interpretation Diffusion Glasses Polymers Models Coherent and Incoherent Scattering Data Treatment The measurement principle of neutron spin echo spectroscopy (quantum mechanical model) • The neutron wave function is split by magnetic fields • The 2 wave packets arrive at magnetic coil 1 magnetic coil 2 polarised sample the sample with a time neutron difference t • If the molecules move between the arrival of the first and second wave packet then coherence is lost • The intermediate scattering t λ3 Bdl function I(Q,t) reflects this ∝ loss in coherence strong wavelength field integral dependence Return The measurement principle of neutron spin echo spectroscopy Dynamic Scattering NSE spectra for diffusive motion Function S(Q,ω) G(R,ω) I(Q,t) = e-t/τ Fourier Transforms temperature up ⇒ τ down Intermediate VanHove