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First observation of excited states in the $^{138}$I nucleus

Abstract : Excited states in the 138I nucleus, including T1/2=1.3 µs isomer decaying by a stretched E2 transition of 68 keV, were observed for the first time. The 138I nucleus was populated in the spontaneous fission of 248Cm and studied by means of prompt gamma-ray spectroscopy using the EUROGAM 2 array. The microsecond isomer was populated in the neutron-induced fission of 235U and observed at the LOHENGRIN separator. Excitation scheme consists of a low-spin part and a medium-spin, DeltaI=1, band based on the 7- state with the (pig7/2nuf7/2)7- dominating configuration, as predicted by the shell model. The shell-model calculations of 138I provide the optimum reproduction of the experimental scheme when the pid5/2 orbital is lowered by 600 keV relative to its position in 133Sb. In the calculation the isomeric level has spin and parity 3- and deexcites by an E2 isomeric transition to the 1- level, located only 9 keV above the predicted 0- ground state. Considering additional information on the ground-state spin from the literature, we propose that in 138I the 1- level corresponds to the ground state and the 0- is located above. We note, however, that additional measurements are required to resolve this problem.
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http://hal.in2p3.fr/in2p3-00147167
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Submitted on : Wednesday, May 16, 2007 - 9:33:16 AM
Last modification on : Thursday, November 19, 2020 - 12:58:50 PM

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T. Rząca-Urban, K. Pągowska, W. Urban, A. Zlomaniec, J. Genevey, et al.. First observation of excited states in the $^{138}$I nucleus. Physical Review C, American Physical Society, 2007, 75, pp.054319. ⟨10.1103/PhysRevC.75.054319⟩. ⟨in2p3-00147167⟩

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