Wave packets comprising a superposition of very-high-lying Rydberg sta
tes have been created using a half-cycle pulse (HCP). The properties o
f the wave packet are probed using a second HCP that is applied follow
ing a variable time delay. The second pulse ionizes a fraction of the
atoms and the survival probability exhibits pronounced oscillations th
at are associated with the quasiperiodic evolution of the wave packet.
Good agreement is found between the experimental data and the results
of a classical trajectory Monte Carlo simulation demonstrating that,
for the times investigated, classical-quantum correspondence holds and
quantum corrections are negligible.