Hollow atoms

Of particular interest is the formation and study of hollow atoms, the accumulation of electrons in shells with high values of principal quantum number n while inner shells remain sparingly populated or empty [84]. 

Double-hole states hollow atoms and triple excitation... 

A hollow atom is any atom for which at least one of the inner shells is completely empty. To produce a hollow atom by exciting only two electrons, the inner shell must therefore be Is2. The simplest hollow atom, and the one which has been known for the longest time is He in a doubly-excited state [310]. One can in principle consider partially hollow atoms, in which only a subshell rather than a complete shell is empty. 

Keywords Electronic correlation Relativistic effects Isotopic effects Multiply excited states Hollow atoms B-spline basis set Charge transfer Photodissociation Radiative association... 

From doubly to multiply excited states in hollow atoms... 

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