Isomeric states in the semimagic 128-130Sn isotopes were populated in the fragmentation of a 136Xe beam on a 9Be target at an energy of 750 A·MeV. The decay of an isomeric state in 128Sn at an excitation energy of 4098 keV has been observed. Its half live has been determined to be T1/2=220(30) ns from the time distributions of the delayed γ rays emitted in its decay. γγ coincidence relations were analyzed in order to establish the decay pattern of the newly established state toward the known (7-) and (10+) isomers at excitation energies of 2092 and 2492 keV, respectively. Based on a comparison with results of state-of-the-art shell-model calculations the new isomeric state is proposed to have the νh11/2-3d3/2-1 configuration with the four neutron holes in 132Sn maximally aligned to a total spin of Iπ=15-.
|Journal||Physical Review C|
|Publication status||Published - 29 Apr 2011|