Lifetimes of unresolved transitions from very high spin states in nuclei nearN=82

Abstract

Average lifetimes of unresolved transitions deexciting very high spin states populated in 2ssi(136'129Xe, xn) 164-x'lsT-XEr reactions have been determined by a Doppler shift attenuation method. We find that the yrast bump region between 1.0 and 1.6MeV contains a majority of strongly collective E2 transitions with very short lifetimes (a few tens of fsec) in the well deformed nuclei around 159Er and, with less certainty, almost comparably short lifetimes in the more spherical nuclei around 152Er. In the high energy region of 2.0-3.2MeV we observe transitions which depopulate longer lived states in the nuclei near N = 82 than in the well deformed systems.

Decay properties of very-high-spin states in transitional Er nuclei aroundA=154

“…Average lifetimes of unresolved transitions have previously been reported for the well deformed nuclides around 16~ [21], and for more spherical ones around 152Er [22]. Enhanced E2 transitions were found in both regions, and this, despite the fact that the Er isotopes exhibit markedly different structures at lower spins, as shown in Fig.…”