The level structures of the very neutron-rich nuclei Pd128 and Pd126 have been investigated for the first time. In the r-process waiting-point nucleus Pd128, a new isomer with a half-life of 5.8(8) μs is proposed to have a spin and parity of 8+ and is associated with a maximally aligned configuration arising from the g9/2 proton subshell with seniority υ=2. For Pd126, two new isomers have been identified with half-lives of 0.33(4) and 0.44(3) μs. The yrast 2+ energy is much higher in Pd128 than in Pd126, while the level sequence below the 8+ isomer in Pd128 is similar to that in the N=82 isotone Cd130. The electric quadrupole transition that depopulates the 8+ isomer in Pd128 is more hindered than the corresponding transition in Cd130, as expected in the seniority scheme for a semimagic, spherical nucleus. These experimental findings indicate that the shell closure at the neutron number N=82 is fairly robust in the neutron-rich Pd isotopes.
Isomers in Pd128 and Pd126 : evidence for a robust shell closure at the neutron magic number 82 in exotic palladium isotopes / H. Watanabe, G. Lorusso, S. Nishimura, Z.Y. Xu, T. Sumikama, P.-A. Soderstrom, P. Doornenbal, F. Browne, G. Gey, H.S. Jung, J. Taprogge, Z. Vajta, J. Wu, A. Yagi, H. Baba, G. Benzoni, K.Y. Chae, F.C.L. Crespi, N. Fukuda, R. Gernhauser, N. Inabe, T. Isobe, A. Jungclaus, D. Kameda, G.D. Kim, Y.K. Kim, I. Kojouharov, F.G. Kondev, T. Kubo, N. Kurz, Y.K. Kwon, G.J. Lane, Z. Li, C.-B. Moon, A. Montaner-PizaK Moschner, F. Naqvi, M. Niikura, H. Nishibata, D. Nishimura, A. Odahara, R. Orlandi, Z. Patel, Z. Podolya, H. Sakurai, H. Schaffner, G.S. Simpson, K. Steiger, H. Suzuki, H. Takeda, A. Wendt, K. Yoshinaga. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 111:15(2013 Oct 11), pp. 152501.1-152501.5.
Isomers in Pd128 and Pd126 : evidence for a robust shell closure at the neutron magic number 82 in exotic palladium isotopes
F.C.L. Crespi;
2013
Abstract
The level structures of the very neutron-rich nuclei Pd128 and Pd126 have been investigated for the first time. In the r-process waiting-point nucleus Pd128, a new isomer with a half-life of 5.8(8) μs is proposed to have a spin and parity of 8+ and is associated with a maximally aligned configuration arising from the g9/2 proton subshell with seniority υ=2. For Pd126, two new isomers have been identified with half-lives of 0.33(4) and 0.44(3) μs. The yrast 2+ energy is much higher in Pd128 than in Pd126, while the level sequence below the 8+ isomer in Pd128 is similar to that in the N=82 isotone Cd130. The electric quadrupole transition that depopulates the 8+ isomer in Pd128 is more hindered than the corresponding transition in Cd130, as expected in the seniority scheme for a semimagic, spherical nucleus. These experimental findings indicate that the shell closure at the neutron number N=82 is fairly robust in the neutron-rich Pd isotopes.
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