  We study how the ionic core in a non-hydrogenic atom modifies the dynamics of
a Rydberg electron in the presence of a weak static external field. We show
that such a system is neither regular nor chaotic: its energy levels display
unusual statistical properties, intermediate between the standard Poisson and
Random Matrix ones. The ionic core acts as a scatterer whose size is comparable
to the de Broglie wavelength of the electron, inducing specific quantum
effects.

Chaotic Dynamics;Chaotic Dynamics