The neutron-rich isotope Sb-136 has been produced following the relativisti
c projectile fission of U-238 in an experiment performed at the Fragment Se
parator at GSI, Darmstadt. Delayed gamma -ray spectroscopy of the fission p
roducts has been performed after isotope separation. A new isomeric state i
n Sb-136 has been populated, and its lifetime measured as T-1/2 = 565(50) n
s. Realistic and empirical shell-model calculations have been performed and
are compared to the experimental observables.