Level structure of light neutron-rich La isotopes beyond the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>N</mi><mo>=</mo><mn>82</mn></mrow></math> shell closure

A. Navin; E. H. Wang; S. Bhattacharyya; Menglan Liu; Cenxi Yuan; M. Rejmund; A. Lemasson; S. Biswas; Y. H. Kim; C. Michelagnoli; J. H. Hamilton; A. V. Ramayya; I. Stefan; R. Banik; P. Bednarczyk; Soumik Bhattacharya; E. Clément; H. L. Crawford; G. de France; P. Fallon; G. Frémont; J. Goupil; B. Jacquot; H. J. Li; J. Ljungvall; Y. X. Luo; A. Maj; L. Ménager; V. Morel; G. Mukherjee; R. Palit; R. M. Pérez-Vidal; J. O. Rasmussen; J. Ropert; C. Schmitt; S. J. Zhu

doi:10.1103/3jvn-hzdh

Level structure of light neutron-rich La isotopes beyond the $N = 82$ shell closure

A. Navin^1,*, E. H. Wang ^2,3,4,†, S. Bhattacharyya ^5,6, Menglan Liu ⁷, Cenxi Yuan ⁷, M. Rejmund¹, A. Lemasson ¹, S. Biswas^1,‡, Y. H. Kim⁸ et al.

C. Michelagnoli ^1,§, J. H. Hamilton ⁴, A. V. Ramayya⁴, I. Stefan ⁹, R. Banik^5,∥, P. Bednarczyk ¹⁰, Soumik Bhattacharya ⁵, E. Clément ¹, H. L. Crawford ¹¹, G. de France ¹, P. Fallon¹¹, G. Frémont¹, J. Goupil¹, B. Jacquot¹, H. J. Li¹, J. Ljungvall ^12,9, Y. X. Luo ^13,4, A. Maj ¹⁰, L. Ménager¹, V. Morel¹, G. Mukherjee ^5,6, R. Palit¹⁴, R. M. Pérez-Vidal ¹⁵, J. O. Rasmussen¹³, J. Ropert¹, C. Schmitt ^1,¶, and S. J. Zhu¹⁶

¹GANIL, CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, BP 55027, F-14076 Caen Cedex 5, France
²Shandong Provincial Key Laboratory of Nuclear Science, Nuclear Energy Technology and Computer Utilization, Weihai Frontier Innovation Institute of Nuclear Technology, School of Nuclear Science, Energy and Power Engineering, Shandong University, Jinan 250061, China
³Weihai Research Institute of Industrial Technology of Shandong University, Weihai 264209, China
⁴Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA
⁵Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata 700064, India
⁶Homi Bhabha National Institute, Training School Complex, Anushaktinagar, Mumbai 400094, India
⁷Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China
⁸Center for Exotic Nuclear Studies, Institute for Basic Science, Daejeon 34126, Republic of Korea
⁹Université Paris-Saclay, CNRS/IN2P3, IJCLab, F-91405 Orsay, France
¹⁰Institute of Nuclear Physics PAN, 31-342 Kraków, Poland
¹¹Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
¹²Université de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France
¹³Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
¹⁴Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai 400005, India
¹⁵Instituto de Física Corpuscular, CSIC–Universitat de València, E-46980 València, Spain
¹⁶Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China

^*Contact author: navin@ganil.fr
^†Contact author: ehwang@sdu.edu.cn
^‡Present address: Rutherford Appleton Laboratory, Fermi Ave, Harwell, Didcot OX11 0QX, United Kingdom.
^§Present address: Institut Laue-Langevin, F-38042 Grenoble Cedex, France.
^∥Present address: Institute of Engineering and Management, Saltlake Sector V, Kolkata 700091, India.
^¶Present address: IPHC Strasbourg, Université de Strasbourg–CNRS/IN2P3, F-67037 Strasbourg Cedex 2, France.

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Phys. Rev. C 112, 044310 – Published 16 October, 2025

DOI: https://doi.org/10.1103/3jvn-hzdh

Abstract

The high spin excited states of Lanthanum isotopes ${}^{140 – 143}{La}$ , above the $N = 82$ closed shell, were populated in fission reactions. The prompt $γ$ -ray transitions were measured using two complementary methods: (a) in coincidence with the isotopically identified fragments produced in the fission of the ${}^{238}U + {}^{9}{Be}$ system using the Variable Mode Spectrometer ( $VAMOS + +$ ) and the Advanced Gamma Tracking Array (AGATA) spectrometer, and (b) high statistics threefold $γ − γ − γ$ and fourfold $γ − γ − γ − γ$ coincidence data from the spontaneous fission of ${}^{252}{Cf}$ using the Gammasphere. This work reports the first identification of a pair of parity doublet structures in ${}^{143}{La}$ and the new high spin level structure in ${}^{140 – 142}{La}$ from prompt $γ$ -ray spectroscopy. The level structures are interpreted in terms of the systematics of neighboring odd- $Z$ nuclei above the $Z = 50$ shell closure and large-scale shell model calculations. The present results indicate the presence of stable octupole deformation in ${}^{143}{La}$ . The excitation energy pattern and their comparison with neighboring isotones, moving away from the $N = 82$ closed shell, point towards a transition from single-particle structures to an alternating parity rotational band structure in the La isotopic chain.

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Level structure of light neutron-rich La isotopes beyond the $N = 82$ shell closure

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Level structure of light neutron-rich La isotopes beyond the N=82 shell closure

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Level structure of light neutron-rich La isotopes beyond the $N = 82$ shell closure