Electronic fluxes during large amplitude vibrations of single, double and triple bonds.

We present a time-dependent quantum mechanical analysis of electronic fluxes during large amplitude vibrations of ethane, ethene and ethyne in the electronic ground state. We find that the number of electrons which participate in the concerted electron-nuclear vibrations decrease from ethane via ethene to ethyne. Different initial conditions and different sets of "observer planes" monitoring the electronic rearrangement are tested to demonstrate the robustness of the results. This counter-intuitive result is due to similar electron distributions of single, double and triple bonds along the carbon-carbon (CC)-axis at equal CC-distances.