VERY-HIGH-N STARK WAVE-PACKETS GENERATED BY AN ELECTRIC-FIELD STEP

Wave packets comprising a coherent superposition of n similar or equal to 390 Stark states have been created in potassium by rapid applicati on of a de field. Their properties are examined using a half-cycle pro be pulse that is applied following a variable time delay and that ioni zes a fraction of the excited atoms. The survival probability exhibits pronounced oscillations (quantum beats) that are associated with the time evolution of the wave packet. Interestingly, even in the present regime of complete overlap of different Stark manifolds, a single domi nant beat frequency is observed, and this is explained quantum mechani cally in terms of energy-level statistics. Similar behavior is predict ed by classical trajectory Monte Carlo simulations that reproduce well the experimental observations demonstrating classical-quantum corresp ondence in high-n systems.