Quadrupole phonons in the cadmium isotopes

A key question concerning the spherical-vibrator attributes of states in cadmium isotopes is addressed by means of a boson Hamiltonian encompassing U(5) partial dynamical symmetry. The U(5) symmetry is preserved in a segment of the spectrum and is broken in particular nonyrast states, and the resulting mixing with the intruder states is small. The vibrational character is thus maintained in the majority of low-lying normal states as observed in 110Cd.