PHASE-SPACE DISTRIBUTIONS AND SPECTRAL PROPERTIES FOR NONHYDROGENIC ATOMS IN MAGNETIC-FIELDS

We present here the first study of the quantum phase-space behaviour ( Wigner functions) for non-hydrogenic atoms in magnetic fields as well as a comprehensive study of spectral properties. We consider primarily an energy regime (scaled energy -0.5) where hydrogen is near-integrab le and hydrogenic wavefunctions would be localized on tori. We find th at the quantum energy level statistics for non-hydrogenic atoms are at the 'chaotic' (Wigner) limit. However, the quantum phase space distri butions, contrary to what one would expect if the underlying classical motion were chaotic, remain dominated by torus-like structures. But t he wavefunctions do explore a larger fraction of phase-space than in t he hydrogenic case where, in the integrable regime, Wigner wavefunctio ns are generally localized on a single torus. Due to the non-semiclass ical nature of the core they are localized on more than one torus; add itional structures other than the tori are also present. Possible inte rpretations of the results in terms of models of the underlying classi cal dynamics are discussed.