New K isomers in the neutron-rich N=100 isotones Sm 162, Eu 163, and Gd 164 NEW K ISOMERS in the NEUTRON-RICH N=100 ... R. YOKOYAMA et al.

R. Yokoyama, S. Go, D. Kameda, T. Kubo, N. Inabe, N. Fukuda, H. Takeda, H. Suzuki, K. Yoshida, K. Kusaka, K. Tanaka, Y. Yanagisawa, M. Ohtake, H. Sato, Y. Shimizu, H. Baba, M. Kurokawa, D. Nishimura, T. Ohnishi, N. IwasaA. Chiba, T. Yamada, E. Ideguchi, T. Fujii, H. Nishibata, K. Ieki, D. Murai, S. Momota, Y. Sato, J. W. Hwang, S. Kim, O. B. Tarasov, D. J. Morrissey, B. M. Sherrill, G. Simpson, C. R. Praharaj

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Abstract

Very neutron-rich Z∼60 isotopes produced by in-flight fission of a 345 MeV/nucleon U238 beam at the RI Beam Factory, RIKEN Nishina Center, have been studied by delayed γ-ray spectroscopy. New isomers were discovered in the neutron-rich N=100 isotones Sm162, Eu163, and Gd164. Half-lives, γ-ray energies, and relative intensities of these isomers were obtained. Level schemes were proposed for these nuclei and the first 2+ and 4+ states were assigned for the even-even nuclei. The first 2+ and 4+ state energies decrease as the proton numbers get smaller. The energies and the half-lives of the new isomers are very similar to those of 4- isomers known in less neutron-rich N=100 isotones Er168 and Yb170. A deformed Hartree-Fock with angular momentum projection model suggests Kπ=4- two-quasiparticle states with ν7/2[633] - ν1/2[521] configurations with similar excitation energy. The results suggest that neutron-rich N=100 nuclei are well deformed and the deformation gets larger as Z decreases to 62. The onset of K isomers with the same configuration at almost the same energy in N=100 isotones indicates that the neutron single-particle structures of neutron-rich isotones down to Z=62 do not change significantly from those of the Z=70 stable nuclei. Systematics of the excitation energies of new isomers can be explained without the predicted N=100 shell gap.

Original languageEnglish
Article number034313
JournalPhysical Review C
Volume95
Issue number3
DOIs
Publication statusPublished - 2017 Mar 15

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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    Yokoyama, R., Go, S., Kameda, D., Kubo, T., Inabe, N., Fukuda, N., Takeda, H., Suzuki, H., Yoshida, K., Kusaka, K., Tanaka, K., Yanagisawa, Y., Ohtake, M., Sato, H., Shimizu, Y., Baba, H., Kurokawa, M., Nishimura, D., Ohnishi, T., ... Praharaj, C. R. (2017). New K isomers in the neutron-rich N=100 isotones Sm 162, Eu 163, and Gd 164 NEW K ISOMERS in the NEUTRON-RICH N=100 ... R. YOKOYAMA et al. Physical Review C, 95(3), [034313]. https://doi.org/10.1103/PhysRevC.95.034313