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New isomers and medium-spin structure of the 95Y nucleus

Abstract : Excited states in 95Y, populated following the spontaneous fission of 248Cm and 252Cf and following fission of 235U induced by thermal neutrons, were studied by means of γ spectroscopy using the EUROGAM2 and GAMMASPHERE multidetector Ge arrays and the LOHENGRIN fission-fragment separator, respectively. We have found a new (17/2−) isomer in 95Y at 3142.2 keV with a half-life of T1/2 = 14.9(5) ns. Another isomer was identified in 95Y at 5022.1 keV and it was assigned a spin-parity (27/2−). For this isomer a half-life of T1/2 = 65(4) ns was determined and four decay branches were found, including an E3 decay. A new E3 decay branch was also found for the known, 1087.5-keV isomer in 95Y, for which we measured a half-life of 51.2(9) μs. The B(E3) and B(E1) transition rates, of 2.0 and 3.8 × 10−7 W.u., respectively, observed in 95Y are significantly lower than in the neighboring 96Zr core, suggesting that octupole correlations in this region are mainly due to the coupling of proton deltaj = 3 orbitals. Shell-model calculations indicate that the (27/2−) isomer in 95Y corresponds to the πg9/2ν(g7/2h11/2) maximally aligned configuration and that all three isomers in 95Y decay, primarily, by M2 transitions between proton g9/2 and f5/2 orbitals.
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Submitted on : Tuesday, April 7, 2009 - 8:32:41 AM
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W. Urban, K. Sieja, G.S. Simpson, H. Faust, T. Rzaca-Urban, et al.. New isomers and medium-spin structure of the 95Y nucleus. Physical Review C, American Physical Society, 2009, 79, pp.044304. ⟨10.1103/PhysRevC.79.044304⟩. ⟨in2p3-00373690⟩



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