Point contact spectroscopy on a H2O molecule bridging Pt electrodes reveals a clear crossover between enhancement and reduction of the conductance due to electron-vibration interaction. As single channel models predict such a crossover at transmission probability of t=0.5, we used shot noise measurements to analyze the transmission and observed at least two channels across the junction where the dominant channel has t=0.51+/-0.01 transmission probability at the crossover conductance, which is consistent with the predictions for single-channel models.
@article{arxiv.0801.3031,
title = {Electron-vibration interaction in single-molecule junctions: from contact to tunneling regime},
author = {O. Tal and M. Krieger and B. Leerink and J. M. van Ruitenbeek},
journal= {arXiv preprint arXiv:0801.3031},
year = {2008}
}