Diffusive motions in liquid medium-chain n-alkanes as seen by quasielastic time-of-flight neutron spectroscopy

Beitrag in einer Fachzeitschrift

Details zur Publikation

Autor(en): Unruh T, Smuda C, Busch S
Zeitschrift: Journal of Chemical Physics
Jahr der Veröffentlichung: 2008
Band: 129
Heftnummer: 12
ISSN: 0021-9606


Different diffusive motions in liquid C(32)H(66) on a picosecond time scale could be disentangled by resolution resolved quasielastic time-of-flight neutron spectroscopy (QENS). It is demonstrated that at all observation times, the dominating motion causes a Q(2) proportionality of the QENS signal, which indicates a Fickian diffusion mechanism. The observed motions can be characterized by an observation time dependent apparent diffusion coefficient D(a)(t(o)), which is up to one order of magnitude larger than the molecular self-diffusion coefficient D(s). By comparison with molecular dynamics simulations, the identified motions are attributed to displacements of hydrogen atoms reflecting not only global but also local molecular trajectories. Despite the rodlike shape of the molecules, the center of mass diffusion was found to be essentially isotropic. A coherent picture of the diffusional processes ranging from the fast tumbling of CH(2) groups to the slow long range molecular diffusion is presented. (C) 2008 American Institute of Physics.

FAU-Autoren / FAU-Herausgeber

Unruh, Tobias Prof. Dr.
Professur für Nanomaterialcharakterisierung (Streumethoden)

Autor(en) der externen Einrichtung(en)
Technische Universität München (TUM)

Zuletzt aktualisiert 2018-08-08 um 03:06