ROLE OF CORE-SCATTERED CLOSED ORBITS IN NONHYDROGENIC ATOMS

While both diamagnetic and Stark spectra of hydrogen can be analyzed a ccurately in terms of classical orbits, in nonhydrogenic atoms the mul tielectron core induces additional spectral modulations that cannot be analyzed reliably in terms of standard periodic orbit-type theories. However, by extending closed-orbit theory to include core-scattered wa ves consistently, both diamagnetic and Stark photoabsorption spectra o f nonhydrogenic Rydberg atoms at constant scaled energy can be analyze d semiclassically using only the closed orbits of the corresponding hy drogenic systems. Frequencies and amplitudes of the core-scattered mod ulations, as well as corrected amplitudes for contributions from repet itions of primitive hydrogenic orbits, are found to be in excellent ag reement with quantum results. We consider whether these nonhydrogenic systems correspond to quantum chaos.