First observation of excited states in the {sup 138}I nucleus.
Excited states in the {sup 138}I nucleus, including T{sub 1/2}=1.3 {micro}s isomer decaying by a stretched E2 transition of 68 keV, were observed for the first time. The {sup 138}I nucleus was populated in the spontaneous fission of {sup 248}Cm 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 {sup 235}U and observed at the LOHENGRIN separator. Excitation scheme consists of a low-spin part and a medium-spin, {Delta}I=1, band based on the 7{sup -} state with the ({pi}g{sub 7/2}{nu}{sub 7/2}{sup f}){sub 7{sup -}} dominating configuration, as predicted by the shell model. The shell-model calculations of {sup 138}I provide the optimum reproduction of the experimental scheme when the {pi}{sub 5/2}{sup d} orbital is lowered by 600 keV relative to its position in {sup 133}Sb. In the calculation the isomeric level has spin and parity 3{sup -} and deexcites by an E2 isomeric transition to the 1{sup -} level, located only 9 keV above the predicted 0{sup -} ground state. Considering additional information on the ground-state spin from the literature, we propose that in {sup 138}I the 1{sup -} level corresponds to the ground state and the 0{sup -} is located above. We note, however, that additional measurements are required to resolve this problem.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); French-Polish IN2P3-KBN Collaboration
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 951048
- Report Number(s):
- ANL/PHY/JA-58867; PRVCAN; TRN: US0902115
- Journal Information:
- Phys. Rev. C, Vol. 75, Issue 2007; ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- ENGLISH
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