Lifetime measurements and nuclear deformation in the A≈100 region

The EUROGAM-2 array has been used to study γ rays emitted following the spontaneous fission of a 248Cm source. Analysis of Doppler-broadened lineshapes corresponding to transitions from excited rotational states in neutron-rich Sr, Zr, Mo, Ru, and Pd fission fragments has enabled measurements of state lifetimes in these nuclei at nuclear spins of I∼10. Extracted transition quadrupole moments are compared with various recent theoretical approaches, as well as with measurements at lower spin, and an interpretation of the data is made within the context of prolate-oblate shape competition in this region. © 2012 American Physical Society.
EUROGAM was funded jointly by IN2P3 (France) and the EPSRC (UK). This work was partly supported by the EPSRC under grant no. GRH71161 and by the the US Department of Energy, Office of Nuclear Physics, under contract no. DE-AC02-06CH11357. The authors are also indebted for the use of 248Cm to the Office of Basic Energy Sciences, US Department of Energy, through the transplutonium element production facilities at the OakRidge National Laboratory. P.S. acknowledges support from MINECO (Spain) under Contract No. FIS2011-23565.