Quadrupole moment of the first 2/sup +/ state of /sup 18/O

By use of SU(3) techniques, a minimal value of the quadrupole moment of the first 2/sup +/ state of /sup 18/O is derived for a two particle model space and a constant effective charge e/sub n/. The influences of state dependent effective charges are discussed. A comparison with experimental measurements yields evidence for the failure of the two-particle model.