By solving the three-dimensional, time-dependent Schrödinger equation, we have demonstrated that the ultrafast charge-transfer process in ion-atom collisions can be mapped out with attosecond extreme uv (xuv) pulses. During the dynamic-charge transfer from the target atom to the projectile ion, the electron coherently populates the two sites of both nuclei, which can be viewed as a “short-lived” molecular state. A probing attosecond xuv pulse can instantly unleash the delocalized electron from such a “transient molecule,” so that the resulting photoelectron may exhibit a “double-slit” interference. On the contrary, either reduced or no photoelectron interference will occur if the attosecond xuv pulse strikes well before or after the collision. Therefore, by monitoring the photoelectron interference visibility, one can precisely time the ultrafast charge-transfer process in atomic collisions with time-delayed attosecond xuv pulses.

• Received 2 September 2010

DOI:https://doi.org/10.1103/PhysRevA.83.041401