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Jeudi 15 décembre 2016 15:00 - Duree : 1 heure
Lieu : Science Building Room 036 - ESRF - 71 avenue des Martyrs - Grenoble

Orateur : Max WOLFF (Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala)

Scattering methods are an extremely powerful tool for the determination of structure, dynamics and excitations in condensed matter physics. Depending on the probe used in such experiments surface or bulk properties can be addressed. Neutrons are characterized by a weak interaction for many engineering materials. As a result they can penetrate deeply into matter and are sensitive to light elements and magnetic induction. As a result neutrons offer an ideal probe for the investigation of soft matter, biological systems, as well as magnetic materials and are complementary to other techniques, like e.g. synchrotron radiation, ion or electron diffraction.

If applied under grazing incidence beam geometry (see figure 1, right panel) neutrons can offer surface sensitivity. If in addition to the specular reflectivity, off-specular scattering or the small angle scattering is collected, correlations in the plane of the interface can be analysed.

After a very brief overview of the activities at the Physics Department and the Material Physics division at Uppsala University I will focus on neutron scattering experiments probing the solid-liquid interface. Recently, it has been demonstrated that the traditionally assumed non-slip boundary condition does not always hold. The discontinuity at the interface can be quantified by a phenomenological number, the slip length (for definition see figure 1, left panel). However, the microscopic origin of slip is still not understood and different scenarios are proposed. Surface sensitive neutron scattering experiments can probe the density profile at the interface as well as lateral correlations or possibly even surface dynamics. Our recent findings, on polymers, self-assembled surfactants and simple liquids, demonstrate that slip in simple liquids can not be explained by a density depleted layer alone. The local structure and dynamics in the liquid at the interface, which are highly sensitive to the interfacial energy, have to be taken into account as well.

Contact : tellier@ill.fr

Discipline évènement : (Physique)
Entité organisatrice : (ILL)
Nature évènement : (Séminaire)
Evènement répétitif : (General ILL Seminar - College 9)
Site de l'évènement : Polygone scientifique

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