Abstract
Background: The neutron-rich Ba isotopes with only six valence protons represent the beginning of the collective rotation-vibration band structure. The sharp shape phase transition at observed in Ce-Gd isotones is not exhibited in , which renders their analysis interesting. Also there are ambiguities in the spin and band assignments.
Purpose: To study their spectra empirically and to compare with predictions from an interacting boson model and microscopic dynamic pairing plus quadrupole model to explain the smooth shape transition at .
Method: We compare the results of the calculation in the interacting boson models (IBM-1) and IBM-2 and the dynamic pairing plus quadrupole model with experiment and illustrate the variation in level structure of the Ba isotopes with N. The absence of sharp phase transition at is examined.
Results: The ambiguous spin and parity of levels of the vibrational bands are assigned on the basis of calculated K components and the decay characteristics.
Conclusion: The second states in have predominance, and states are . The smooth transition at is explained.
1 More- Received 11 January 2015
- Revised 12 April 2015
DOI:https://doi.org/10.1103/PhysRevC.91.054312
©2015 American Physical Society