A New Class of Atomic States: The 'Wannier-ridge' Resonances

The evidence for the existence of systems that are dominated by electron-electron correlations is briefly reviewed, with particular attention being paid to (i) the processes of near-threshold electronimpact ionization and excitation of atoms and (ii) the structure of atomic doubly excited states and Feshbach resonances. New evidence is then presented for the existence of atomic resonances in which two excited electrons both have high val. es of the principal quantum number n (up to n = 8), and in which these two electrons reside on or near the Wannier ridge (i.e. with r1 ~ -rz).