21 July 1994 Coverage-dependent diffusion of ammonia on Re(001)
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Proceedings Volume 2125, Laser Techniques for Surface Science; (1994) https://doi.org/10.1117/12.180856
Event: OE/LASE '94, 1994, Los Angeles, CA, United States
Abstract
Diffusion of ammonia on Re(001) was studied utilizing optical second harmonic diffraction from surface coverage grating. The diffusion process at initial coverages NH3/Re>0.15 could be simulated only if coverage dependent diffusion constant has been considered. The resulting diffusivity D((theta) )equalsD0 exp(-Em((theta) )/RT), is defined by a barrier for diffusion Em((theta) )equalsE0-(omega) Z(theta) , with activation energy at zero coverage E0equals3.4+/- 0.8 kcal/mol, D0equals2.8(DOT)10-3cm2sec- 1. The repulsion energy between pair of nearest neighbor molecules of (omega) equals0.4+/- 0.06 kcal/mol is obtained if an average of three nearest neighbors is assumed at the edge of the grating. The coverage effect on the diffusivity is found to correlate quantitatively with dipole-dipole repulsion between nearest neighbors. This results in a constant corrugation ratio Ediff/Edes, over the entire coverage range.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Micha Asscher, Micha Asscher, } "Coverage-dependent diffusion of ammonia on Re(001)", Proc. SPIE 2125, Laser Techniques for Surface Science, (21 July 1994); doi: 10.1117/12.180856; https://doi.org/10.1117/12.180856
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