Identification of a Shape Isomer in 235U
Journal article, 2007
The shape isomer in 235U has been searched for in a neutron-induced fission experiment on 234U, which was performed at the isomer spectrometer NEPTUNE of the EC-JRC IRMM. A neutron source, with a tunable pulse frequency in the Hz to kHz range and its individually adjustable neutron pulse width in connection with an appropriate detector system turned out to be the ideal instrument to perform an isomer search, when decay half-lives above 100 µs are expected. From the delayed fission events observed for two different NEPTUNE settings and at mean incident neutron energies En=0.95 and 1.27 MeV the isomeric fission half-life could be determined to be T1/2=(3.6±1.8) ms. The corresponding cross section was determined to sigma_if=(10±8) µb. With these results an experimental confirmation for the existence of a superdeformed shape isomer in odd-uranium isotopes is given for the first time.