Hi All, I've just been reading the paper with the following reference: Nashner, M. S.; Frenkel, A. I.; Adler, D. L.; Shapley, J. R.; Nuzzo, R. G. Structural Characterization of Carbon-Supported Platinum - Ruthenium Nanoparticles from the Molecular Cluster. J. Am. Chem. Soc. 1997, 7863, 7760-7771. In particular I was interested about the data analysis section on page 7763 (footnote 32) where the authors talk about time reversibility of multiple scattering paths. It is mentioned that the collinear DS path, in the fcc structure, (M - M(1) - M(4) - M) is time reversed, so has twice the degeneracy, but that the collinear TS path (M - M(1) - M(4) - M(1) - M) is not time reversed. Why is the DS path time reversible, but not the TS path despite the apparent 'symmetry' of the TS path? What makes a scattering path time reversible? Does time reversibility only apply to collinear paths or can it also apply to triangular paths as well? Thanks for your help, David David W Inwood PhD Researcher Chemistry University of Southampton Southampton, UK SO17 1BJ