Generator-coordinate representation of the O(4) supermultiplets of doubly excited states

The O(4) supermultiplets of doubly excited states of atoms are analyzed and reexpressed in a generator-coordinate representation. It is explicitly shown that a complete separation of the collective and internal motions is realized in the high-excitation limit. A new explicit expression for the collective vibration in terms of quasispin operators is also derived. Particular emphasis is put on the close relation between the group-theoretical supermultiplet classification and the mean-field theoretical approach.