ABSTRACT
In preceding sections it was mentioned that additional quantum numbers are needed to distinguish between states with the same symmetry type of the spatial functions which have the same value of L. In ln configurations some of these quantum numbers are supplied by the seniority scheme. We saw that the seniority scheme is based on the group O(2l + 1) which is intermediate between U(2l + 1) and O(3), namely U(2l + 1) ⊃ O(2l + 1) ⊃ O(3). When more than one l-orbit is active, no such intermediate groups are generally known. There is, however a special case in which a simple scheme was found. We shall briefly describe this case in which there is theoretical interest. The theory of this case is due to Elliott (1958). Many papers have been written on the Elliott scheme and it would be difficult to list them here.
