NONDISPERSIVE ELECTRONIC WAVE-PACKETS IN MULTIPHOTON PROCESSES

We describe how the nonlinear coupling between the unperturbed Coulomb motion of a Rydberg electron and a linearly polarized microwave field may create an electronic wave packet of almost ''eternal'' lifetime, evolving according to the classical equations of motion without disper sion. This new quantum object owes its existence to the underlying mix ed regular chaotic structure of classical phase space and is experimen tally accessible.