Excitation of a Three-Dimensionally Localized Atomic Electron Wave Packet

We have prepared an atomic electron in a three-dimensionally localized wave packet that travels along a highly eccentric orbit between the nucleus and a turning point approximately 1000 Å away. State preparation consisted of two distinct steps. First the electron wave function was localized to the desired orbit by exciting a stationary extreme Stark state from the $n=30\mathrm{}$ manifold of a sodium atom in a dc electric field. Then the dynamic wave packet was formed by applying a terahertz electromagnetic half-cycle pulse polarized along the direction of the dc field. The localized state is an ideal starting point for further quantum control proceeding along classical orbits.