Identification of μs isomers in the fission products of241Pu(nth,f)

Abstract

Several $\ensuremath{\mu}\mathrm{s}$ isomers were observed in neutron-rich nuclei in the mass range $A=88--109.$ These nuclei are produced by thermal neutron-induced fission of ${}^{241}\mathrm{Pu}.$ The detection is based on time correlation between fission fragments selected by the LOHENGRIN spectrometer, at ILL (Grenoble) and the $\ensuremath{\gamma}$-ray or conversion electron emission of the isomers. Among a dozen isomers studied, three new ones have been observed. The decay schemes of ${}^{88m}\mathrm{Br},$ ${}^{94m}\mathrm{Y},$ ${}^{96m}\mathrm{Rb},$ and ${}^{100m}\mathrm{Nb}$ are discussed in the framework of the spherical shell model. The yields and isomeric ratios of all these isomers have been measured.