K isomerism in $^{255}$Rf and total kinetic energy measurements for spontaneous fission of $^{255,256,258}$Rf
Résumé
Spontaneous fission properties of the isotopes Rf255, Rf256, and Rf258 produced in the reactions Ti50+Pb207, Ti50+Pb208, and Ti50+Bi209 were studied. The method of time and position correlations was used to identify spontaneous fission events. The correction to the energy deficit in measured total kinetic energy (TKE) determined on the basis of a study of No252 was applied to evaluate the TKE¯ of investigated rutherfordium isotopes. A signature which we assigned tentatively to bimodal fission was observed in TKE distributions of Rf255 and Rf256. Two new high-K isomeric states in Rf255 were identified by ER-CE-(CE)-α/SF correlation search, with half-lives of 38−7+12 and 15−4+6 μs at excitation energies 1150–1450 and 900–1200 keV, respectively. Including those metastable states a tentative partial level scheme was proposed.
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