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Decay spectroscopy of neutron-rich ¹²⁹Cd with the GRIFFIN spectrometer Saito, Yukiya


Nuclei around doubly magic ¹³²Sn are of particular interest in nuclear structure as well as nuclear astrophysics. Their properties provide important input for the r-process as waiting-point nuclei. For example, their shell structure and half-lives affect the shape of the second r-process abundance peak at A∼130. In terms of nuclear structure, the evolution of single-particle levels near shell closures is ideal for testing the current nuclear models far from stability. There have been two studies on the decay of ¹²⁹Cd, however, the level schemes of ¹²⁹In have large discrepancies. Also, many of the spins of the excited states remain unclear. Therefore, the main purpose of the present study is to resolve the disagreements in the reported level schemes and to determine the properties of the energy states. The experiment was performed at the ISAC facility of TRIUMF, Canada. A 480 MeV proton beam, which was accelerated by the main cyclotron at TRIUMF, was impinged on an uranium carbide target to produce radioactive isotopes. ¹²⁹Cd was extracted using the Ion Guide Laser Ion Source (IG-LIS). γ-rays following the decays of ¹²⁹Cd were detected with the GRIFFIN spectrometer comprising of 16 high-purity germanium (HPGe) clover type detectors, along with the β-particles detected with SCEPTAR. The high statistics and the high sensitivity of the detectors allowed us to perform detailed and precise spectroscopy. A theoretical calculation was conducted using the shell model code NuShellX@MSU, employing the realistic residual interaction model jj45pna. The results of the analysis, including 29 new transitions and 5 new excited states, will be discussed and compared to the theoretical calculations.

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