Recoil distance method lifetime measurement of the 21+ state in Sr94 and implications for the structure of neutron-rich Sr isotopes
AbstractA high precision lifetime measurement of the 21+ state in Sr94 was performed at TRIUMF's ISAC-II facility by coupling the recoil distance method implemented via the TIGRESS integrated plunger with unsafe Coulomb excitation in inverse kinematics. Due to limited statistics imposed by the use of a radioactive Sr94 beam, a likelihood ratio χ2 method was derived and used to compare experimental data to Geant4 simulations. The B(E2;21+→01+) value extracted from the lifetime measurement of 7.80−0.40+0.50(stat.)±0.07(sys.) ps is approximately 25% larger than previously reported while the relative error has been reduced by a factor of approximately 8. A baseline deformation has been established for Sr isotopes with N≤58 which is a necessary condition for the quantum phase transition interpretation of the onset of deformation in this region. A comparison to existing theoretical models is presented.