Tuesday, 14 November 1:00pm – 2:00pm

This seminar will be delivered in Chemistry Lecture Theatre 4

Speaker: Reiner Zorn, Forschungszentrum Jülich GmbH

Host: Prof. Peter Harrowel

Title: The length scale of the dynamics of glass-forming liquids studied by neutron scattering

Abstract: In this talk I will give an overview of what quasielastic and inelastic neutron scattering can contribute to the question of an immanent length scale of the dynamics in glass-forming liquids. In the first part, I will present experiments where the problem is tackled by confining the liquids to a size similar to that of the presumed length scale. It turns out that effects are visible but overlayed by an interfacial deceleration of the dynamics which makes it difficult to interpret the results unambiguously. These effects can be reduced by the use of ‘soft’ confinement where the interface is not rigid. In addition to the effect on the main (α) relaxation, the vibrational spectrum scan be studied in the glassy state. The latter experiments may hint at the origin of the so-called ‘boson peak’. In the second part of the talk, I will present a more recently proposed method to determine the length scale from a combination of quasielastic neutron scattering with dynamic calorimetry. In contrast to the former approach, this works in the bulk but is experimentally challenging because of the seemingly disparate dynamic ranges of the methods. The results indicate that it is necessary to consider temperature fluctuations in the thermodynamical treatment of such systems.

Bio: https://www.fz-juelich.de/profile/zorn_r