Observation of Inner Electron Ionization from Radial Rydberg Wave Packets in Two-Electron Atoms

We have observed multiphoton ionization of the 5s core electron from a 5snd radial Rydberg wave packet of Sr atoms using a short optical pulse. When the outer nd electron is at its outer turning point the inner 5s electron is removed from the atom, and the outer electron is left in a Sr+ Rydberg state, but when the outer electron is at the inner turning point this does not occur. Analysis of the final Sr+ Rydberg states shows that the two electrons interact as the inner electron leaves, so that the outer electron is not simply projected onto the Sr+ Rydberg states.