Shape coexistence in $^{96,98}$Sr

International audience; The structure of neutron-rich 96,98Sr isotopes was investigated by lowenergyCoulomb excitation of radioactive beams at the REX-ISOLDE facility.Reduced transition probabilities and spectroscopic quadrupole moments wereextracted from the differential Coulomb excitation cross sections. These results allowfor the first time to draw definite conclusions about the shape coexistence of highlydeformed prolate and spherical configurations. In particular, a very small mixingbetween the coexisting states is observed, contrary to other mass regions wherestrong mixing is the rule. The experimental data suggest a significant contribution ofthe triaxial degree of freedom in the ground state of both isotopes. In addition,experimental information on low-lying states in 98Rb has been obtained.