Several $\mu \mathrm{s}$ isomers were observed in neutron-rich nuclei in the mass range $A=88\mathrm{}–109.$ 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 $\gamma$-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.

• Received 17 February 1998

DOI:https://doi.org/10.1103/PhysRevC.59.82