Proceedings of the workshop “Probing Dynamics at Interfaces–Options for Inelastic Neutron Reflectometry”

Dynamic phenomena in solid matter can show drastically different behaviour if the system dimensions are reduced. Diffusion and fluctuations in confined structures or at interfaces can be decreased by orders of magnitude, the damping effectively changing the interaction with surrounding media, or even enhanced as found in low dimensional magnetic structures. Up to now neutrons have been used to investigate the dynamics in such systems mainly by classical inelastic time of flight spectroscopy, e.g. the analysis of water diffusion in layered systems, or by applying off-specular neutron reflectivity to elucidate fluctuations in layered systems such as polymer layers, smectic liquid crystals or phospholipid membranes. The application of neutron reflectometry to study not only the structure and lateral organisation of layered systems and interfaces but also the dynamic features have been so far restricted, mainly due to the low flux of current neutron sources. One possibility to do so, neutron spin echo reflectometry, has gained new interest as an option to study the structure and dynamic in layered systems and at interfaces (see recent work by Rekveldt [1,2], Pynn [3] and Felcher [4]). It was proposed to exploit Larmor precession techniques to extract dynamic information by neutron reflectometry and the feasibility of this approach was demonstrated in very recent experiments at HMI and ILL [3–6]. In addition, a first neutron spin echo reflectometry-like measurement of the dynamics in smectic liquid membranes has been recently successfully carried out on IN15 at ILL [7]. It should be mentioned that the principal possibility to perform neutron reflectometry measurements with a classical inelastic time of flight spectroscopy set-up was acknowledged some years ago in Dubna [8]. Inelastic neutron reflectometry would open up a complete new field in the analysis of dynamic phenomena by neutron techniques in various fields such as magnetic multilayers, polymer layers, biomembranes, solid–liquid interfaces and any interface-related system. It would provide new and complementary information to methods like X-ray photoelectron correlation spectroscopy, EXAFS and NMR. Dedicated instruments for inelastic neutron reflectometry could be implemented within the planned instruments at the new neutron