High-spin states above the isomers in neutron-rich iodine nuclei near N=82

Abstract

Excited states of neutron-rich iodine isotopes I130–134 above the high-spin isomers have been identified using prompt-delayed γ-ray spectroscopy. The iodine isotopes were produced as fission fragments of fusion-fission and transfer induced fission of Be9(U238,f) at a beam energy of 6.2 MeV/u. The complete (A,Z) identification was obtained using the large acceptance magnetic spectrometer VAMOS++. The AGATA γ-ray tracking array was used to detect the prompt γ rays while the delayed γ rays (in the time range of 100 ns to 200 μs) from the isomeric states were identified by the EXOGAM segmented clover detectors, placed behind the focal plane of the VAMOS++ spectrometer. The high-spin states above the (8−) isomers in I130,132 were populated for the first time, and a new isomer in I132 was identified. A new γ-ray transition was also assigned to the level structure of I134. Prompt transitions above the 19/2− isomer were identified in I131,133, for the first time. The level structures are interpreted in terms of the systematics of odd-Z nuclei above the Z=50 shell closure and large-scale shell model calculations.11 MoreReceived 13 May 2020Accepted 9 October 2020DOI:https://doi.org/10.1103/PhysRevC.102.044329©2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectromagnetic transitionsIsomer decaysNuclear structure & decaysShell modelProperties90 ≤ A ≤ 149Nuclear Physics