Half-life of the 15/2$^+$ state of $^{135}$I : A test of E2 seniority relations

International audience; The half-life of the 15/2+1 state of the 3-valence-proton nucleus 135I has been measured to be 1.74(8) ns using the EXILL-FATIMA mixed array of Ge and LaBr3 detectors. The nuclei were produced following the cold neutron-induced fission of a 235U target at the PF1B beam line of the Institut Laue-Langevin. The extracted B(E2;15/2+→11/2+) value enabled a test of seniority relations for the first time between E2 transition rates. Large-scale shell-model calculations were performed for 134Te and 135I, and reinterpreted in a single-orbit approach. The results show that the two-body component of the E2 operator can be large whereas energy shifts due to the three-body component of the effective interaction are small.