First observation of excited states in the {sup 138}I nucleus
- Faculty of Physics, Warsaw University, ul.Hoza 69, 00-681 Warsaw (Poland)
- Laboratoire de Physique Subatomique et de Cosmologie, IN2P3-Centre National de la Recherche Scientifique/Universite Joseph Fourier, F-38026 Grenoble Cedex (France)
- Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700064 (India)
- Department of Physics, Bengal Engineering and Science University, Shibpur, Howrah 711103 (India)
- Institut Laue-Langevin, B.P. 156, F-38042 Grenoble Cedex 9 (France)
- Department of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom)
- Argonne National Laboratory, Argonne, Illinois 60439 (United States)
Excited states in the {sup 138}I nucleus, including T{sub 1/2}=1.3 {mu}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}f{sub 7/2}){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}d{sub 5/2} 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.
- OSTI ID:
- 20995281
- Journal Information:
- Physical Review. C, Nuclear Physics, Vol. 75, Issue 5; Other Information: DOI: 10.1103/PhysRevC.75.054319; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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