Long-Period Orbits in the Stark Spectrum of Lithium

We report observation of the signature of very-long-period orbits in the Stark spectrum of lithium in a regime of classical chaos. We identify recurrences associated with the orbits parallel to the electric field, including those beyond the 100th return of the primitive orbit. We also identify recurrences due to scattering of an incoming wave from one orbit into another by the alkali-metal core.