Open Access

Dipole Strength Distribution of ${}^{8}{He}$ and Decay Characteristics

C. Lehr ¹, T. Aumann ^1,2,3, M. Duer ^1,*, A. T. Saito⁴, T. Nakamura ⁴, N. L. Achouri ⁵, D. Ahn⁶, H. Baba ⁶, S. Bacca ⁷ et al.

C. A. Bertulani ⁸, M. Böhmer ⁹, F. Bonaiti ^7,10,11, K. Boretzky ², C. Caesar ^1,2,6, N. Chiga ⁶, D. Cortina-Gil¹², C. A. Douma ¹³, F. Dufter ⁹, Z. Elekes ^14,15, J. Feng¹⁶, B. Fernández-Domínguez ¹², U. Forsberg¹⁷, N. Fukuda⁶, I. Gasparic ^18,1,6, Z. Ge ⁶, R. Gernhäuser ⁹, J. M. Gheller¹⁹, J. Gibelin ⁵, A. Gillibert¹⁹, K. I. Hahn ^20,21, Z. Halász ¹⁴, M. N. Harakeh ¹³, A. Hirayama⁴, M. Holl ¹, N. Inabe⁶, T. Isobe ⁶, J. Kahlbow ¹, N. Kalantar-Nayestanaki ¹³, D. Kim²¹, S. Kim ^21,1, T. Kobayashi^22,†, Y. Kondo⁴, D. Körper², P. Koseoglou ¹, Y. Kubota ⁶, P. J. Li ^23,24, S. Lindberg ²⁵, Y. Liu¹⁶, F. M. Marqués ⁵, S. Masuoka²⁶, M. Matsumoto⁴, J. Mayer ²⁷, K. Miki ^1,22, M. Miwa⁶, B. Monteagudo⁵, A. Obertelli ^1,19, N. A. Orr ⁵, H. Otsu⁶, V. Panin^6,2, S. Y. Park^20,21, M. Parlog⁵, S. Paschalis ^17,1, P. M. Potlog ²⁸, S. Reichert ⁹, A. Revel ^5,29,10,30, D. M. Rossi ¹, R. Roth ¹, M. Sasano⁶, H. Scheit ¹, F. Schindler¹, T. Shimada⁴, S. Shimoura ²⁶, H. Simon ², S. Storck Dutine ¹, L. Stuhl ^21,26, H. Suzuki⁶, D. Symochko¹, H. Takeda⁶, S. Takeuchi⁴, J. Tanaka ^1,6, Y. Togano ⁴, T. Tomai⁴, H. T. Törnqvist ^1,2, J. Tscheuschner¹, T. Uesaka⁶, V. Wagner ¹, H. Yamada⁴, B. Yang¹⁶, L. Yang²⁶, Z. H. Yang⁶, M. Yasuda⁴, K. Yoneda⁶, L. Zanetti¹, and J. Zenihiro ^6,31

¹Technische Universität Darmstadt, Fachbereich Physik, 64289 Darmstadt, Germany
²GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, 64291 Darmstadt, Germany
³Helmholtz Forschungsakademie Hessen für FAIR, Max-von-Laue-Strasse 12, 60438 Frankfurt, Germany
⁴Department of Physics, Institute of Science Tokyo, 2-12-1 O-Okayama, Meguro, Tokyo 152-8551, Japan
⁵Université de Caen Normandie, ENSICAEN, IN2P3/CNRS, LPC-Caen UMR6534, F-14000 Caen, France
⁶RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako 351-0198, Japan
⁷Institut für Kernphysik and PRISMA + Cluster of Excellence, Johannes Gutenberg-Universität, 55128 Mainz, Germany
⁸Department of Physics and Astronomy, East Texas A&M University, Commerce, Texas 75429, USA
⁹Technische Universität München, Physik Department, 85748 Garching, Germany
¹⁰Facility for Rare Isotope Beams, Michigan State University, East Lansing, Michigan 48824, USA
¹¹Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
¹²Departamento de Física de Partículas, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
¹³Nuclear Energy group, ESRIG, University of Groningen, 9747 AA Groningen, The Netherlands
¹⁴HUN-REN ATOMKI, P.O. Box 51, H-4001 Debrecen, Hungary
¹⁵Institute of Physics, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, H-4032 Debrecen, Hungary
¹⁶State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China
¹⁷School of Physics, Engineering and Technology, University of York, York YO10 5DD, United Kingdom
¹⁸Rudjer Bošković Institute, Zagreb, Croatia
¹⁹IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
²⁰Ewha Womans University, Seoul 03760, Korea
²¹Center for Exotic Nuclear Studies, Institute for Basic Science, Daejeon 34126, Korea
²²Department of Physics, Tohoku University, Miyagi 980-8578, Japan
²³Department of Physics, The University of Hong Kong, Hong Kong, China
²⁴Key Laboratory of Nuclear Physics and Ion-Beam Application (MOE), Institute of Modern Physics, Fudan University, Shanghai 200433, China
²⁵Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
²⁶Center for Nuclear Study, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
²⁷Universität zu Köln, Institut für Kernphysik, Zülpicher Straße 77, 50937 Köln, Germany
²⁸Institute of Space Sciences, 077125 Magurele, Romania
²⁹GANIL, CEA/DRF-CNRS/IN2P3, 14076 Caen, France
³⁰Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
³¹Department of Physics, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto 606-8502, Japan

^*Contact author: mduer@ikp.tu-darmstadt.de
^†Deceased.

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Phys. Rev. Lett. 136, 172501 – Published 1 May, 2026

DOI: https://doi.org/10.1103/vp3m-5rpp

Abstract

The weak binding and spatially extended neutron densities characteristic of drip-line nuclei give rise to a distinctive low-energy dipole response. The drip-line nucleus ${}^{8}{He}$ is the most neutron-rich bound nucleus with a mass-to-charge ratio of $A / Z = 4$ . We measure the dipole response of ${}^{8}{He}$ , including for the first time the four-neutron decay channel. A total dipole strength of $\sum B (E 1) (E^{*} < 15 MeV) = 0.95 (16) e^{2} {fm}^{2}$ and a dipole polarizability of $α_{D} = 0.61 (1) {fm}^{3}$ are extracted from the differential Coulomb-excitation cross section and compared to state-of-the-art theoretical calculations employing coupled cluster and three-body approaches. We find that the dipole continuum is dominated, even at high excitation energies well above the $4 n$ decay threshold, by two-neutron emission, pointing to a ${}^{6}{He} + 2 n$ structure of the excited dipole mode. No indication was found for a $4 n$ final-state correlation, while pronounced $n n$ and ${}^{6}{He} − n$ final-state correlations are apparent.

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Phys. Rev. Lett. 136, 172501– Published 1 May, 2026

Vol. 136, Iss. 17 — 1 May 2026

Received 19 January 2026
Accepted 20 March 2026

DOI: https://doi.org/10.1103/vp3m-5rpp

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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Dipole Strength Distribution of ${}^{8}{He}$ and Decay Characteristics

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Dipole Strength Distribution of He8 and Decay Characteristics

Abstract

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References (48)

Dipole Strength Distribution of ${}^{8}{He}$ and Decay Characteristics