Fission and gamma-ray decay of the238U shape isomer

Abstract

The decay of the 238U 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 the 238mu recoils, produced in a 238U(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 in 238U. 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 fission T1;2 =(298 _+ 18) ns. PACS" 23.20.Ck; 23.20.Lv; 25.85.Ge; 27.90. + b

Shell effects in superdeformed minima

“…Experimental data are taken from Ref [44]. ( 236 U; 2.75 MeV),[45,46] ( 238 U; 2.56 MeV), and[47,46] ( 240 Pu; 2.8 MeV). Only an approximate value is known for 240 Pu.…”