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Direct observation of 𝛽 and 𝛾 decay from a high-spin long-lived isomer in 187 Ta

Chen, J. L. [Beihang Univ. (China)] (ORCID:000900031275394X)·Watanabe, H. [Beihang Univ. (China); RIKEN Nishina Center (Japan); High Energy Accelerator Research Organization (KEK) (Japan)] (ORCID:0000000274469595)·Walker, P. M. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0000000294413011)·Hirayama, Y. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000294851177)·Watanabe, Y. X. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000324257188)·Mukai, M. [Univ. of Tsukuba (Japan); RIKEN Nishina Center (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)]·Jiao, C. F. [Sun Yat-Sen Univ., Guangzhou (China)] (ORCID:0000000252925158)·Ahmed, M. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Univ. of Tsukuba (Japan)] (ORCID:0000000170643878)·Brunet, M. [Univ. of Surrey, Guildford (United Kingdom)]·Hashimoto, T. [Institute for Basic Science (IBS) (Korea, Republic of)]·Ishizawa, S. [RIKEN Nishina Center (Japan); Yamagata Univ. (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000312660148)·Kondev, F. G. [Argonne National Laboratory (ANL), Argonne, IL (United States)] (ORCID:0000000295675785)·Lane, G. J. [Australian National Univ., Canberra (Australia)] (ORCID:000000032244182X)·Litvinov, Yu. A. [GSI-Helmholtzzentrum fur Schwerionenforschung, Darmstadt (Germany)] (ORCID:0000000270434993)·Miyatake, H. [Univ. of Tsukuba (Japan); RIKEN Nishina Center (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000268888507)·Moon, J. Y. [Institute for Basic Science (Korea, Republic of)] (ORCID:0000000162574286)·Niwase, T. [RIKEN Nishina Center (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Kyushu Univ., Fukuoka (Japan)] (ORCID:0000000200542278)·Park, J. H. [Institute for Basic Science (Korea, Republic of)]·Podolyák, Zs. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0000000260949520)·Rosenbusch, M. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000251991073)·Schury, P. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000270946761)·Wada, M. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Univ. of Tsukuba (Japan)] (ORCID:000000033109759X)·Xu, F. R. [Peking University, Beijing (China)] (ORCID:0000000166990965)
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Abstract

187 Ta (Z = 73, N = 114) is located in the neutron-rich A ≈ 190 region where a prolate-to-oblate shape transition via triaxial softness is predicted to take place. A preceding work on the K π = (25/2 - ) isomer and a rotational band to which the isomer decays carried out by the same collaboration revealed that axial symmetry is slightly violated in this nucleus. Here, this paper focuses on a higher-lying isomer, which was previously identified at 2933(14) keV by mass measurements with the Experimental Storage Ring at GSI. The isomer of interest has been populated by a multinucleon transfer reaction with a 136 Xe primary beam incident on a natural tungsten target, using the KEK Isotope Separation System at RIKEN. New experimental findings obtained in the present paper include the internal and external β-decay branches from the high-spin isomer and a revised half-life of 136(24) s. The evaluated hindrances for K-forbidden transitions put constraints on the spin-parity assignment, which can be interpreted as being ascribed to a prolate shape with a five-quasiparticle configuration by model calculations.

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BibTeXRIS

Chen, J. L. [Beihang Univ. (China)] (ORCID:000900031275394X), Watanabe, H. [Beihang Univ. (China); RIKEN Nishina Center (Japan); High Energy Accelerator Research Organization (KEK) (Japan)] (ORCID:0000000274469595), Walker, P. M. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0000000294413011), Hirayama, Y. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000294851177), Watanabe, Y. X. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000324257188), Mukai, M. [Univ. of Tsukuba (Japan); RIKEN Nishina Center (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)], Jiao, C. F. [Sun Yat-Sen Univ., Guangzhou (China)] (ORCID:0000000252925158), Ahmed, M. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Univ. of Tsukuba (Japan)] (ORCID:0000000170643878), Brunet, M. [Univ. of Surrey, Guildford (United Kingdom)], Hashimoto, T. [Institute for Basic Science (IBS) (Korea, Republic of)], Ishizawa, S. [RIKEN Nishina Center (Japan); Yamagata Univ. (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000312660148), Kondev, F. G. [Argonne National Laboratory (ANL), Argonne, IL (United States)] (ORCID:0000000295675785), Lane, G. J. [Australian National Univ., Canberra (Australia)] (ORCID:000000032244182X), Litvinov, Yu. A. [GSI-Helmholtzzentrum fur Schwerionenforschung, Darmstadt (Germany)] (ORCID:0000000270434993), Miyatake, H. [Univ. of Tsukuba (Japan); RIKEN Nishina Center (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000268888507), Moon, J. Y. [Institute for Basic Science (Korea, Republic of)] (ORCID:0000000162574286), Niwase, T. [RIKEN Nishina Center (Japan); High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Kyushu Univ., Fukuoka (Japan)] (ORCID:0000000200542278), Park, J. H. [Institute for Basic Science (Korea, Republic of)], Podolyák, Zs. [Univ. of Surrey, Guildford (United Kingdom)] (ORCID:0000000260949520), Rosenbusch, M. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000251991073), Schury, P. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)] (ORCID:0000000270946761), Wada, M. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan); Univ. of Tsukuba (Japan)] (ORCID:000000033109759X), Xu, F. R. [Peking University, Beijing (China)] (ORCID:0000000166990965). 2025-01-03. Direct observation of 𝛽 and 𝛾 decay from a high-spin long-lived isomer in 187 Ta. https://doi.org/10.1103/physrevc.111.014304

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