The beta -decays of Sr and Y isotopes in the mass chains 96, 98, 100 and the level schemes of their Y and Zr daughters

The fission product separators JOSEF at the Kernforschungsanlage Julich, Germany and LOHENGRIN at the Institut Laue-Langevin, Grenoble, France were used for the investigation of the beta -decays and the level schemes of short-lived Sr, Y and Zr isotopes with A=96, 98 and 100 which lie at the onset of the deformed region. The beta -spectra, singles gamma -ray spectra, prompt and delayed gamma , gamma ; beta , gamma and e/sup -/, gamma coincidences were measured. The half-lives of the decays of /sup 96/Sr, /sup 96/Y, /sup 98/Sr, /sup 98/Y and /sup 100/Y were determined. Isomeric beta -decaying states were found in /sup 96/Y and /sup 98/Y, they are interpreted as due to the neighbourhood of the p/sub 1/2/, g/sub 9/2/ proton shells and the s /sub 1/2/, g/sub 7/2/ neutron shells in this mass region. The level schemes of /sup 96/Y, /sup 96/Zr, /sup 98/Y, and /sup 100/Zr were established or extended. While the existence of a rotational-like cascade in /sup 98/Y is confirmed, there is no evidence for the coexistence of spherical and deformed nuclear shapes in /sup 96/Zr and /sup 98/Zr. In /sup 100/Zr the known rotational like cascade was also found after the beta -decay of /sup 100/Y. A low lying excited 0/sup + / state was found in this nucleus in analogy to the even Zr-isotopes with lower mass.