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Mass Transport in Surface Diffusion of van der Waals Bonded Systems: Boosted by Rotations?

Hedgeland, Holly; Sacchi, Marco; Singh, Pratap; McIntosh, Andrew J.; Jardine, Andrew P.; Alexandrowicz, Gil; Ward, David J.; Jenkins, Stephen J.; Allison, William and Ellis, John (2016). Mass Transport in Surface Diffusion of van der Waals Bonded Systems: Boosted by Rotations? The Journal of Physical Chemistry Letters, 7(23) pp. 4819–4824.

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Mass transport at a surface is a key factor in heterogeneous catalysis. The rate is determined by excitation across a translational barrier and depends on the energy landscape and the coupling to the thermal bath of the surface. Here we use helium spin−echo spectroscopy to track the microscopic motion of benzene adsorbed on Cu(001) at low coverage (θ ∼ 0.07 ML). Specifically, our combined experimental and computational data determine both the absolute rate and mechanism of the molecular motion. The observed rate is significantly higher by a factor of 3.0 ± 0.1 than is possible in a conventional, point-particle model and can be understood only by including additional molecular (rotational) coordinates. We argue that the effect can be described as an entropic contribution that enhances the population of molecules in the transition state. The process is generally relevant to molecular systems and illustrates the importance of the pre-exponential factor alongside the activation barrier in studies of surface kinetics.

Item Type: Journal Item
Copyright Holders: 2016 American Chemical Society
ISSN: 1948-7185
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: Physics
Item ID: 47808
Depositing User: Holly Hedgeland
Date Deposited: 15 Nov 2016 09:21
Last Modified: 02 Jun 2019 12:26
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