Observation of electron tunneling by Doppler electron spectroscopy

The mirror symmetry of diatomic homonuclear molecules gives rise to electron tunneling between the two indistinguishable atomic sites of the molecule. So far, this tunneling time has been determined solely by the energy splitting between the gerade and ungerade symmetry states due to parity conservation of the electromagnetic interaction. Here we report on the first determination of the tunneling time in a diatomic homonulear molecule by an alternative method, the electron emission asymmetry of the Doppler shifted electrons in the molecular frame of the dissociating molecule. This is a quasi time resolved method. The result is in good agreement with the known symmetry splitting of the final ionic state of the decaying dissociating molecule.