Regensburg 2019 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 32: Complex Fluids and Soft Matter (joint session DY/CPP)
DY 32.15: Talk
Wednesday, April 3, 2019, 19:00–19:15, H3
MIEZE spectroscopy of sub-picosecond collective dynamics in bulk liquid water — Olaf Soltwedel1,2, •Leonie Spitz3, Johanna K Jochum3,4, Andreas Wendl1, Christian Pfleiderer1, and Christian Franz3 — 1Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany — 2Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany — 3Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany — 4Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
The anomalously large dielectric constant of water is intimately connected with a Debye relaxation peak in low frequency dielectric spectra. Despite intense research, a link between the molecular dynamics and the Debye relaxation peak, are still under heavy debate. Proposed mechanisms include translational and/or rotational motions, movement of free water molecules, collective relaxation of a cluster or hopping of defects in the hydrogen bond network. We used MIEZE (Modulation IntEnsity with Zero Effort) neutron spin echo spectroscopy, a high resolution time of flight technique, to measure the dynamic structure factor (S(q,t)) of water over an exceptional dynamical range (0.01 up to 1000ps). Consistent with the literature, we find the bulk transverse diffusion on length scales from 0.1/Å up to 0.4/Å. As our main result, reveals at least two more processes on sub-picosecond time-scales. This provides direct evidence of a vibration and/or delocalization of hydrogen larger than the intermolecular distance as proposed [1].
[1] A. Arbe et al. PRL 117, 185501 (2016)