## Abstract

Lifetimes of high-spin states in ^{164}Yb have been measured by the Doppler-broadened line shape (DBLS) method using the reaction ^{124}Sn(^{44}Ca, 4n)^{164}Yb at a bombarding energy of 189 MeV. The Q_{t} values from the data decrease sharply over the rotational frequency range 0.3 to 0.5 MeV (I = 20 to 32 ℏ). At the same rotational frequencies the kinematic moment of inertia is nearly constant, increasing slightly at the higher frequencies ℏω = 0.40 to 0.55 MeV. These observations can be understood qualitatively as a rotationally-induced deoccupation of strongly shape polarizing anti-aligned high-j, low-Ω orbitals i.e., those in which the nucleons are moving in the opposite direction to the rotation. A summary of the Q_{t} values extracted from the lifetime data for the yrast decay sequences of the even-A nuclei ^{160-168}Yb are compared with the deformations from self-consistent cranking TRS calculations. The TRS calculations show the expected neutron number dependence, i.e., Δβ_{2}/β_{2}(ℏω = 0) is smaller with increasing N and the corresponding loss of collectivity, Q_{t} vs ℏω, has a smaller slope at the larger ℏω with increasing N. For ^{164,166,168}Yb the loss of collectivity from the DBLS measurements occurs at higher ℏω than predicted and the slope of Q_{t}, vs ℏω is much larger than predicted. The enhanced E1/E2 branching ratios and the large transition dipole moments for decay of the states in the (-, 1) band to the ground band and the (+, 0) band in ^{164}Yb suggest an octupole instability for ^{164}Yb.

Original language | English |
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Pages (from-to) | 560-578 |

Number of pages | 19 |

Journal | Nuclear Physics A |

Volume | 599 |

Issue number | 3-4 |

DOIs | |

State | Published - Mar 25 1996 |

## Keywords

- Measured Iγ, γ-γ-γ coincidence spectra
- Measured lifetimes of high-spin states by the DBLS method
- Nuclear reactions Sn(Ca, 4n)Yb, E = 189 MeV

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