Experimental search for the symmetric double-<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>α</mi></math> decay in <math xmlns="http://www.w3.org/1998/Math/MathML"><mmultiscripts><mi>Rn</mi><mprescripts></mprescripts><none></none><mrow><mn>216</mn><mo>,</mo><mn>218</mn></mrow></mmultiscripts></math> and <math xmlns="http://www.w3.org/1998/Math/MathML"><mmultiscripts><mi>Ra</mi><mprescripts></mprescripts><none></none><mrow><mn>220</mn><mo>,</mo><mn>222</mn></mrow></mmultiscripts></math>

L. Heitz; Ch. Theisen; E. Khan; M. Vandebrouck; D. Thisse; B. Sulignano; T. Chaminade; V. Girard-Alcindor; M. Assié; B. Blank; D. Beaumel; J. Bequet; Y. Blumenfeld; D. Cotte; T. Davinson; D. Desforges; T. Dickel; J.-P. Ebran; J. Giovinazzo; C. Houarner; H. Jacob; K. Johnston; M. Kowalska; U. Köster; I. D. Moore; V. Morel; L. Nies; A. Ortega-Moral; I. Pohjalainen; T. Roger; F. Saillant; M. Simonov; L. Thulliez; G. Toccabens; H. Wilsenach

doi:10.1103/5pmf-nxdg

Experimental search for the symmetric double- $α$ decay in ${}^{216, 218}{Rn}$ and ${}^{220, 222}{Ra}$

L. Heitz ^1,2,*, Ch. Theisen^1,†, E. Khan^2,3, M. Vandebrouck¹, D. Thisse¹, B. Sulignano¹, T. Chaminade¹, V. Girard-Alcindor², M. Assié² et al.

B. Blank⁴, D. Beaumel², J. Bequet¹, Y. Blumenfeld², D. Cotte¹, T. Davinson⁵, D. Desforges¹, T. Dickel^6,7, J.-P. Ebran^8,9, J. Giovinazzo⁴, C. Houarner¹⁰, H. Jacob², K. Johnston¹¹, M. Kowalska¹¹, U. Köster¹², I. D. Moore¹³, V. Morel¹⁰, L. Nies¹¹, A. Ortega-Moral⁴, I. Pohjalainen¹³, T. Roger¹⁰, F. Saillant¹⁰, M. Simonov^14,7, L. Thulliez¹, G. Toccabens¹, and H. Wilsenach^15,16,7

¹Université Paris-Saclay, CEA, IRFU, 91191 Gif-sur-Yvette, France
²IJCLab, Université Paris-Saclay/IN2P3-CNRS, F-91406 Orsay Cedex, France
³Institut Universitaire de France (IUF)
⁴LP2i Bordeaux, UMR5797, Université de Bordeaux, F-33170 Gradignan, France
⁵SUPA, School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, EH9 3FD Edinburgh, United Kingdom
⁶GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany
⁷II. Physikalisches Institut, Justus-Liebig-Universität, Heinrich-Buff-Ring 16, 35392 Gießen, Germany
⁸CEA, DAM, DIF, 91297 Arpajon, France.
⁹Université Paris-Saclay, CEA, Laboratoire Matière en Conditions Extrêmes, 91680 Bruyères-le-Châtel, France
¹⁰GANIL, CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, BP 55027, F-14076 Caen, France
¹¹Physics Department, CERN European Organization for Nuclear Research, CH-1211 Geneva 23, Switzerland
¹²Institut Laue Langevin, 71 Avenue des Martyrs, 38042 Grenoble, France
¹³Department of Physics, Accelerator Laboratory, University of Jyvaskyla, P.O. Box 35(YFL), FI-40014 University of Jyvaskyla, Finland
¹⁴Helmholtz Forschungsakademie Hessen für FAIR (HFHF), Campus Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany
¹⁵Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
¹⁶School of Physics and Astronomy, Tel Aviv University, 6997801 Tel Aviv, Israel

^*Present address: CEA, DAM, DIF, 91297 Arpajon, France.
^†Deceased.

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Phys. Rev. C 114, 014337 – Published 30 July, 2026

DOI: https://doi.org/10.1103/5pmf-nxdg

Abstract

The symmetric double- $α$ decay of ${}^{216, 218}{Rn}$ and ${}^{220, 222}{Ra}$ has been investigated at the ISOLDE facility. Radioactive molecular ${}^{220, 222}{RaF}$ ion beams were produced and delivered at an energy of 30 keV with intensities of approximately $10^{3}$ and $10^{5} pps$ , respectively. The ions were implanted into a thin self-supported carbon foil surrounded by four double-sided silicon strip detectors. Three ${}^{14}C$ cluster emission events from ${}^{222}{Ra}$ were observed. The measured branching ratio, $B = [10 . 1_{- 6.4}^{+ 7.8} (stat) \pm 1.1 (syst)] \times 10^{- 10}$ , is consistent with the adopted value. For the simultaneous symmetric double- $α$ decay ( $E_{α_{1}} = E_{α_{2}}$ and $θ_{α_{1} α_{2}} = 180^{\circ}$ ), no excess events were observed in the region of interest. Consequently, experimental upper limits on the branching ratios were derived at the level of $10^{- 7}$ and $10^{- 9}$ for the ${}^{220}{Ra}$ and ${}^{222}{Ra}$ decay chains, respectively.

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Experimental search for the symmetric double- $α$ decay in ${}^{216, 218}{Rn}$ and ${}^{220, 222}{Ra}$

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Experimental search for the symmetric double-α decay in Rn216,218 and Ra220,222

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Experimental search for the symmetric double- $α$ decay in ${}^{216, 218}{Rn}$ and ${}^{220, 222}{Ra}$