# New isomer in $^{96}$Y marking the onset of deformation at N = 57

Abstract : The level scheme of 96Y was significantly extended and a new 201 ns isomer was located at 1655 keV excitation energy, with spin-parity assignment of 5± or 6−. The isomer decays to spherical low-spin structure by transitions with large hindrance and is fed by a short cascade which resembles the beginning of a rotational band. This is in analogy with the feeding and decay pattern of the 4− isomer in 98Y, here confirmed, by lifetime analysis, as a bandhead of a rotational structure with sizable deformation. It is suggested that the new isomer in 96Y arises from a shape change between deformed and spherical configurations, which indicates the appearance of deformation already at N = 57 in the yttrium chain. The experimental findings for 96Y are strengthened by theoretical calculations based on the complex Excited Vampir model.

Cited literature [7 references]

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### Citation

W. Iskra, B. Fornal, S. Leoni, G. Bocchi, A. Petrovici, et al.. New isomer in $^{96}$Y marking the onset of deformation at N = 57. EPL - Europhysics Letters, European Physical Society/EDP Sciences/Società Italiana di Fisica/IOP Publishing, 2017, 117 (1), pp.12001. ⟨10.1209/0295-5075/117/12001⟩. ⟨in2p3-01481899⟩

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