Abstract
Self-conjugate nuclei in the A≈70–80 region have attracted a great deal of attention due to phenomena such as shape coexistence and increasing collectivity along the N=Z line. We investigate the structure of nuclei in this region through lifetime measurements using the GRETINA array. The first implementation of the Differential Recoil Distance Doppler Shift technique with fast radioactive beams is demonstrated and verified through a measurement of the well-known B(E2;21+→01+) transition strength in 74Kr. The method is then applied to determine the B(E2;21+→01+) transition strength in 74Rb, the heaviest odd–odd N=Z nucleus for which this quantity has been determined. This result and extended systematics along N=Z suggest the dominance of the isoscalar part of the quadrupole transition strengths in self-conjugate nuclei, as well as the possible presence of shape coexistence in 74Rb.
Highlights
Nuclei along the N = Z line offer a unique opportunity to study nuclear structure
We report the measurement of the 2+1 -state lifetime in the odd–odd N = Z nucleus 74Rb
Because the Differential Recoil Distance Doppler Shift (DRDDS) method does not make reference to the fast-peak population I f, it is possible to choose the distance between the target and first degrader such that the feeding states have all decayed before reaching the first degrader
Summary
Nuclei along the N = Z line offer a unique opportunity to study nuclear structure. Being symmetric with respect to the isospin degree of freedom, these systems offer an ideal setting in which to study isospin symmetry breaking effects, for example through the differences in the excitation energies of isobaric analogue states in an isospin multiplet [1]. The odd–odd N = Z nuclei are interesting in this regard, as a competition can arise between the isoscalar (T = 0) and isovector (T = 1) pairing modes.
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