Self-diffusion in molecular liquids: medium-chain n-alkanes and coenzyme Q10 studied by quasielastic neutron scattering.
A systematic time-of-flight quasielastic neutron scattering (TOF-QENS) study on diffusion of n-alkanes in a melt is presented for the first time. As another example of a medium-chain molecule, coenzyme Q(10) is investigated in the same way. The data were evaluated both in the frequency and in the time domain. TOF-QENS data can be satisfactorily described by different models, and it turned out that the determined diffusion coefficients are largely independent of the applied model. The derived diffusion coefficients are compared with values measured by pulsed-field gradient nuclear magnetic resonance (PFG-NMR). With increasing chain length, an increasing difference between the TOF-QENS diffusion coefficient and the PFG-NMR diffusion coefficient is observed. This discrepancy in the diffusion coefficients is most likely due to a change of the diffusion mechanism on a nanometer length scale for molecules of medium-chain length.
Smuda
Christoph
C
Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universitat Munchen, Lichtenbergstrasse 1, D-85747 Garching b. Munchen, Germany.
Busch
Sebastian
S
Gemmecker
Gerd
G
Unruh
Tobias
T
D000473:Alkanes / Q000737:chemistry*; D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy; D033363:Neutron Diffraction; D015203:Reproducibility of Results; D013816:Thermodynamics; D013997:Time Factors; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000737:chemistry
D000473:Alkanes; D014451:Ubiquinone; C024989:coenzyme Q10