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In the A = 100 region, the dramatic shape change observed for Zr [1-3] and Sr [4-7] (Z = 40 and 38, respectively) is not present in Kr (Z = 36) isotopes [8-10]. The ${2}^{+}_{1}$ energies and the B(E2;${2}^{+}_{1}$ $\rightarrow$ ${0}^{+}_{1}$) values vary smoothly across the Kr isotopes. This is in contrast to the Sr and Zr isotopes which display a large jump at N = 60, indicating a significant increase in the ground state deformation of these isotopes. The ${\nu}g_{7/2}$ orbital is filled in the ground states of krypton isotopes around N = 59 and is thought to lower the energy of the ${\pi}g_{9/2}$ orbital and help to drive deformation in this region.
Previous studies in this region have shown a smooth onset of deformation in Kr isotopes at N = 60 [9,10], and evidence of a new oblate structure coexisting with the prolate ground state [11]. Accurately predicting ground-state spins and parities of odd-mass isotopes in this region is challenging due to the large valence space, and lack of ESPE data and accurate shell-model interactions. The single-particle energy differences and spectroscopic factors extracted from neutron adding reactions will provide a more complete experimental picture of the underlying single-particle configurations allowing for comparison to modern shell-model calculations [12] that try to describe the onset of deformation around A = 100.
The transfer reactions $^{92,94}$Kr$\textit{(d,p)}$ were carried out in inverse kinematics at an energy of 7.35 MeV/u using the ISOLDE Solenoidal Spectrometer at ISOLDE, CERN. However, due to the low yield obtained for the $^{94}$Kr beam, only the $^{92}$Kr$\textit{(d,p)}$ reaction has been performed so far. Spectroscopic factors of the low-lying states of $^{93}$Kr have been determined. Preliminary results obtained in the October 2022 experiment will be presented.
References
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