Fission and gamma-ray decay of the238U shape isomer
The decay of the238U superdeformed shape isomer has been reinvestigated by detecting for the first time simultaneously the fission and the gamma-back decay. An electrostatic deflection system has been used to transport the238mU recoils, produced in a238U(d, pn) reaction with a pulsed beam of 18 MeV deuterons, in front of a detector set-up consisting of three ion-implanted solidstate detectors and a Ge(Li) gamma-detector. The gamma-back decay has been measured in coincidence with conversion electrons of the 2+ → 0+ transition deexciting the first rotational state in238U. Two gamma-transitions of 2.513 MeV and 1.878 MeV have been observed with half-lives consistent with the result obtained for the decay by delayed fissionT1/2=(298±18) ns.