Lifetime measurement of the 2(1)(+) state in Rb-74 and isospin properties of quadrupole transition strengths at N = Z

Self-conjugate nuclei in the A approximate to 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;2(1)(+) -> 0(1)(+)) transition strength in Kr-74. The method is then applied to determine the B(E2; 2(1)(+) -> 0(1)(+)) transition strength in Rb-74, 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 Rb-74. (C) 2018 The Author(s). Published by Elsevier B.V.