Abstract
Many of the Cd-48 nuclei are good examples of U(5) or vibrational nuclei. Like the Sn-50 nuclei and others in the region, states exist which are interpreted in terms of the excitation of a pair of protons across the shell gap (intruders). The features of the comparatively well-understood Cd nuclei will be considered and compared with the Te-52 nuclei where intruders have not been identified experimentally and problems exist with the U(5) interpretation.