Lifetime measurements in ¹³¹Sb at LOHENGRIN

The neutron-rich (131) Sb nucleus was studied at Institut Laue-Langevin, with the LOHENGRIN spectrometer, via neutron-induced fission of (235) U and lifetime measurements using LaBr3(Ce) detectors. The lifetimes of the 11/2(1)(+) and 19/2(1)(+) states were measured with the generalized centroid difference and the decay slope methods, yielding T-1/2=3(2) ps and T-1/2=1347(171) ps, respectively. The measured value for the 11/2(1)(+) is at the limit of the fasttiming technique. The level scheme of (131) Sb and the decay properties of the 11/2(1)(+) state were described by realistic shell-model calculations, which reproduce well both the experimental spin and energy sequences of Sb-131 and the measured B(E2;11/2(1)(+). 7/2(1)(+)) value, pointing to an almost pure 2(+)(Sn-130) circle times pi g(7/2), core-proton coupled configuration for the 11/2(1)(+) state.