Stability of transuranic and transfermium isomers: single-particle structure implications and decays

W. M. Seif; A. R. Abdulghany

doi:10.1140/epja/s10050-025-01726-y

2024 Impact factor 2.8

Hadrons and Nuclei

Eur. Phys. J. A (2025) 61: 269
https://doi.org/10.1140/epja/s10050-025-01726-y

Regular Article - Theoretical Physics

Stability of transuranic and transfermium isomers: single-particle structure implications and $α$ $\alpha$ decays

W. M. Seif¹^,2^,3^a and A. R. Abdulghany¹

¹ Faculty of Science, Department of Physics, Cairo University, 12613, Giza, Egypt
² Joint Institute for Nuclear Research, 141980, Dubna, Russia
³ The Academy of Scientific Research and Technology, Cairo, Egypt

^a wseif@sci.cu.edu.eg

Received: 1 August 2025
Accepted: 24 October 2025
Published online: 24 November 2025

Abstract

The transuranic-transfermium region ( $Z \geq 92$ $Z \ge 92$ ) hosts 221 known isomers across 160 isotopes. We examine their single-particle configurations and $α$ $\alpha$ -decay stability relative to ground states. Our analysis reveals that proton or neutron shell/subshell closures enhance isomer production and stabilize high-spin multi-quasiparticle configurations by strengthening couplings between complementary valence nucleons. Evidenced deformed sub-shell closure at $Z = 96$ $$Z=96$$ [ $Z = 104$ $$Z=104$$ ] boosts isomer yields attributed to occupations in $π 5 / 2^{+} [642] (1 i_{13 / 2^{+}})$ $\pi 5/2^+[642](1i_{13/2^+})$ , $π 5 / 2^{-} [523] (1 h_{9 / 2^{-}})$ $\pi 5/2^-[523](1h_{9/2^-})$ and $π 7 / 2^{+} [633] (1 i_{13 / 2^{+}})$ $\pi 7/2^+[633](1i_{13/2^+})$ [ $π 9 / 2^{+} [624] (1 i_{13 / 2^{+}})$ $\pi 9/2^+[624](1i_{13/2^+})$ , $π 1 / 2^{-} [521] (2 f_{5 / 2^{-}})$ $\pi 1/2^-[521] (2f_{5/2^-})$ and $π 7 / 2^{-} [514] (1 h_{9 / 2^{-}})$ $\pi 7/2^-[514](1h_{9/2^-})$ ] orbitals. A neutron deformed shell gap at $N = 152$ $$N=152$$ promotes isomerism in $N = 151, 153$ $$N=151,153$$ isotones, primarily through $ν 5 / 2^{+} [622] (1 i_{11 / 2^{+}})$ $\nu 5/2^+[622](1i_{11/2^+})$ , $ν 11 / 2^{-} [725] (1 j_{15 / 2^{-}})$ $\nu 11/2^-[725](1j_{15/2^-})$ , and $ν 9 / 2^{-} [734] (1 j_{15 / 2^{-}})$ $\nu 9/2^-[734](1j_{15/2^-})$ excitations. The leading quasi-particle configurations in the isomers of $N = 147$ $$N=147$$ –149 isotones originate from neutrons/holes in the $ν 7 / 2^{+} [624] (2 g_{9 / 2^{+}})$ $\nu 7/2^+[624](2g_{9/2^+})$ and $ν 1 / 2^{+} [631] (3 d_{5 / 2^{+}})$ $\nu 1/2^+[631] (3d_{5/2^+})$ orbitals. The most stable isomers are predominantly driven by excitations in the $π 1 i_{13 / 2^{+}}$ $\pi 1i_{13/2^+}$ and $ν 1 j_{15 / 2^{-}}$ $\nu 1j_{15/2^-}$ orbitals, under moderate prolate deformation, with key contributions from the $π 11 / 2^{+} [615]$ $\pi 11/2^+[615]$ , $π 9 / 2^{+} [624]$ $\pi 9/2^+[624]$ , $π 7 / 2^{+} [633]$ $\pi 7/2^+[633]$ , $π 5 / 2^{+} [642]$ $\pi 5/2^+[642]$ , $ν 11 / 2^{-} [725]$ $\nu 11/2^-[725]$ , $ν 9 / 2^{-} [734]$ $\nu 9/2^-[734]$ , and $ν 7 / 2^{-} [743]$ $\nu 7/2^-[743]$ states, then from deformed states of the $π 2 f_{7 / 2^{-}}$ $\pi 2f_{7/2^-}$ and $ν 1 i_{11 / 2^{+}}$ $\nu 1i_{11/2^+}$ orbitals. Unlike heavier transfermiums, isomers (iso) of the Np–Es isotopes ( $N = 127$ $$N=127$$ –144 isotones) exhibit no $α$ $\alpha$ -decays. The limited data constrain ${log}_{10} T_{α}^{(iso)}$ $\log _{10} T_{\alpha }^{\text {(iso)}}$ to a single linear trend versus $\sqrt{Q_{α}^{- 1}}$ $\sqrt{Q_{\alpha }^{-1}}$ for favored and unfavored decays, unlike the ground-state decays where the trend’s slope correlates with the transferred angular momentum ( $Δ l$ $\Delta l$ ), with stability enhanced against high- $Δ l$ $\Delta l$ decays. The $α$ $\alpha$ -preformation factor in isomers $S_{α}^{(iso)}$ $S_{\alpha }^{\text {(iso)}}$ exceeds ground-state (gs) value only when $Q_{α}^{(iso)} \leq Q_{α}^{(gs)}$ $Q_{\alpha }^{\text {(iso)}} \le Q_{\alpha }^{\text {(gs)}}$ and $Δ l$ $\Delta l$ is low; otherwise, $S_{α}^{(iso)}$ $S_{\alpha }^{\text {(iso)}}$ drops by 1–3 orders of magnitude, decreasing with both $Q_{α}^{(iso)}$ $Q_{\alpha }^{\text {(iso)}}$ and $Δ l$ $\Delta l$ . This study reveals transactinide isomers as a promising research direction for finding stable configurations in undiscovered superheavy nuclei.

Copyright comment Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Communicated by Chong Qi.

© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

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Stability of transuranic and transfermium isomers: single-particle structure implications and α decays

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Stability of transuranic and transfermium isomers: single-particle structure implications and $α$ $\alpha$ decays