[en] We continue the study of strongly correlated atomic systems along two lines: (1) electron correlations of doubly excited states; (2) charge transfer, excitation and ionization in ion-atom collisions. This abstract summarizes the progress made since the last contractors' workshop at NBS and the programs currently underway

[en] This report summarizes the progress made in our study of strongly correlated systems since the last DOE/BES Atomic Physics Program Workshop and addresses our future plans. The report is divided into two parts: the study of electron correlations and the classification of multiply excited states of atoms; the theroetical study of charge transfer processes in ion-atom collisions

[en] This report discusses research of doubly excited states of atoms and positive ions, and ion-atom collisions

[en] In this review the application of hyperspherical coordinates is discussed for the solution of some of the typical atomic and molecular problems, and the new physical insights obtained from such studies are shown. In particular, it is shown how correlations between two excited electrons can be conveniently understood in terms of the surface harmonics at a constant hyperradius and visualized by displaying the surface charge densities on the angular coordinates that describe radial and angular correlations. It is shown that a new set of correlation quantum numbers K, T and A for any two-electron states can be deduced by analyzing the surface harmonics; here K and T describe angular correlation and A = +1, -1 or 0) describes radial correlation. Because of the isomorphic correlations, states which have A = +1 or -1 are shown to exhibit supermultiplet structure while states which have A = 0 are shown to behave like singly excited states. Therefore this classification scheme includes the independent particle approximation as a subset. The relations of these quantum numbers to the collective vibrations and rotations of molecule-like normal modes are also discussed. Applications of hyperspherical harmonics to the three-body breakup and linear triatomic collisions are also discussed briefly. 57 refs., 15 figs

[en] During the reported period we continued the study of basic atomic 3-body problems along two lines: (1) the understanding of radial and angular correlations between two excited electrons; and (2) calculations of reliable excitation, ionization and charge transfer cross sections in ion-atom collisions from intermediate to low energies. In item (2), we have modified our so-called AO+ code to include ionization channels (represented by pseudostates), so that excitation, ionization and charge transfer are all incorporated in our model. This is a necessary step since all these processes are coupled for ion-atom collisions at intermediate velocities. In item (1), we have made further progress in understanding the correlation patterns of two highly excited electrons. We have examined the conventional configuration-interaction approach for doubly excited states and have compared it with our adiabatic approximation in hyperspherical coordinates. We have also made some preliminary study in understanding the Stark effects of H^- resonances and generalized the hyperspherical coordinates approach to two-valence-electron systems like Li^- and Be

[en] Recent theoretical development in the understanding of electron transfer processes is reviewed. K-K electron transfer processes are studied for projectiles (nuclear charge Z/sub B/) and targets (nuclear charge Z/sub A/) in which Z/sub A/ and Z/sub B/ range from Z/sub A/ much greater than Z/sub B/ to Z/sub A/ approx. = Z/sub B/, over the energy range 0.1 < v/v/sub e/ < 2

[en] The theory of electron capture in multielectron ion-atom collisions based upon the atomic expansion method for collisions at a few keV/amu to a few MeV/amu is considered. Single-electron transfer processes are primarily considered. First-order perturbation theories for charge transfer, the K--K electron capture cross sections in heavy ion-atom collisions, the differential cross sections for electron transfer, electron capture from L- and M-subshells, quasi-molecular binding correction to the atomic expansion method, and further improvement of the theoretical model are treated. 25 references

[en] Studies of electron correlations of doubly-excited electrons in hyperspherical coordinates, and differential and total cross sections for charge transfer and ionization in fast ion-atom collisions are reported

[en] Current development of the theory of electron transfer in ion-atom collisions is summarized. Preliminary results indicate that K-K capture cross sections at lower energies are sensitive to the proper treatment of the atomic model. It was shown that electron capture from outer shells of multielectron atoms can be calculated using the present method, in conjunction with the simple independent electron model. Some recent research is summarized. 8 references

[en] This report discusses: the study of coulombic 3-body systems in hyperspherical coordinates; further studies of electron correlations in doubly excited states of atoms; and theoretical studies of ion-atom collisions