Observation of a nondecaying wave packet in a two-electron atom

We excite and manipulate wave packets in the Rydberg states of atomic calci um. The manipulation is via the electron-electron correlations between a co re electron and the Rydberg electron and mediated by a strong excitation of the core transition. Striking changes in the wave packet are observed part icularly when the Rabi oscillations of the core transition are synchronized with the natural, classical oscillation frequency of the Rydberg wave pack et. In that case, the wave packet is shaped into a form that inhibits decay or autoionization as demonstrated by a coherent probe of the resulting wav e packet. This work impacts on both coherent control and quantum measuremen t studies.