Revealing the tunneling-ionization initial position of oriented molecules with a temporal double-slit interferometer.

The tunneling of a particle through a barrier is one of the most fundamental and ubiquitous quantum processes. The rapid progress in strong-field physics enables us to resolve the laser-induced tunneling ionization from atoms and molecules at a more precise level. Here we employ a temporal double-slit interferometer to probe the electron wave packet generated from the strong-field-induced tunneling of a molecule. By rotating the molecular orientation angle relative to the polarization direction of the laser field, we find that the phase of the electron wave packet at the tunnel exit is modified, leading to a shift of the temporal double-slit interference fringe in the photoelectron momentum distribution. Based on the molecular strong-field approximation, we establish a relation between the phase of the electron wave packet and the tunneling-ionization initial position of the molecule, allowing us to retrieve the tunneling-ionization initial position of the molecule for different orientations from the temporal double-slit interference patterns. We also find the angular-resolved ionization rate of the molecule directly correlates with the tunneling-ionization initial position.