NOVEL DYNAMIC SYMMETRIES OF ASYMMETRICALLY DOUBLY EXCITED 2-ELECTRON ATOMS

We study a new class of long-lived resonances of doubly excited two-electron atoms. The states are characterized by a highly polarized inner electron located near the axis between the nucleus and a dynamically localized outer electron. Classical mechanics studies prove the stability of the corresponding classical motion and allow for EBK quantization to obtain semiclassical energies. The resonance states are treated further within the framework of a single-channel adiabatic approximation, where the inner electron is prescribed by a polarized molecular type wavefunction. The adiabatic energies as well as the semiclassical results are in good agreement with resonance energies obtained by highly accurate solutions of the full three-body Schrodinger equation. There is a one-to-one correspondence between approximate quantum numbers derived from the semiclassical and from the adiabatic approach, both of which explain the nodal structures of the ab initio quantum wavefunctions reflecting the approximate dynamical symmetries of the problem. Decay mechanisms and the resulting widths of the resonances are discussed. The dependence of these configurations on the nuclear charge Z is examined.