Interplay of collective and noncollective modes in low-lying quadrupole states of ¹⁴⁰Ba, ¹⁴²Ce, ¹⁴⁴Nd and ¹⁴⁶Sm

The low-lying quadrupole excited states in ¹⁴⁰Ba, ¹⁴²Ce, ¹⁴⁴Nd and ¹⁴⁶Sm are investigated using the quasiparticle-phonon model. The microscopic structure of these levels is analysed and the relevant spectroscopic quantities are calculated and compared with experiment. It is found that the interaction between collective and noncollective modes leads to a complex structure for the second and third 2⁺ states. While the first 2⁺ state is an isoscalar one, the second and third 2⁺ states have a large isovector component.