Shape transition in the neutron-rich Y nuclei and its evolution across the isotopic chain

¹ INFN sezione di Milano via Celoria 16, 20133, Milano, Italy
² Institute of Nuclear Physics, PAN, 31–342, Krakow, Poland
³ Dipartimento di Fisica, Università degli Studi di Milano, I–20133, Milano,
⁴ ILL, 71 Avenue des Martyrs, 38042, Grenoble CEDEX 9, France

^* Corresponding author: lukasz.iskra@mi.infn.it

Published online: 4 December 2019

Abstract

The evolution of the deformation across the Y isotopic chain, in the vicinity of N = 60 boundary, has been studied using gamma spectroscopy methods. The nuclei of interest have been produced by neutron induced fission of ²³⁵U and ²⁴¹Pu targets, during two experimental campaigns named EXILL and FIPPS at the Institute Laue-Langevin in Grenoble. The emitted gamma rays have been collected by HPGe and LaBr₃ detectors providing the identification of the high-spin levels in the ⁹⁴Y and ⁹⁶Y isotopes up to 6 MeV excitation energy, as well as information about the half-lives of the in-band states in the ⁹⁸Y nucleus. The obtained results shed new light on the onset of deformation in the neutron-rich Y isotopes and, in general, in the A ≈ 100 region.