Beyond the Neutron Drip-Line: The Unbound Oxygen Isotopes 25O and 26O

C. Caesar (1; 2); J. Simonis (1; 3); T. Adachi (4); Y. Aksyutina; (2; 3); J. Alcantara (5); S. Altstadt (6); H. Alvarez-Pol (5); N. Ashwood; (7); T. Aumann (1; 2); V. Avdeichikov (8); M. Barr (7); S. Beceiro (5); D.; Bemmerer (9); J. Benlliure (5); C. A. Bertulani (10); K. Boretzky (2); M.J.G.; Borge (11); G. Burgunder (12); M. Caamano (5); E. Casarejos (13); W. Catford; (14); J. Cederk\"all (8); S. Chakraborty (15); M. Chartier (16); L. Chulkov; (17; 3); D. Cortina-Gil (5); U. Datta Pramanik (15); P. Diaz Fernandez; (5); I. Dillmann (2); Z. Elekes (9); J. Enders (1); O. Ershova (6); A.; Estrade (2; 18); F. Farinon (2); L.M. Fraile (1; 9); M. Freer (7); M.; Freudenberger (1); H.O.U. Fynbo (20); D. Galaviz (21); H. Geissel (2); R.; Gernh\"auser (22); P. Golubev (8); D. Gonzalez Diaz (1); J. Hagdahl (23); T.; Heftrich (6); M. Heil (2); M. Heine (1); A. Heinz (23); A. Henriques (21); M.; Holl (1); J.D. Holt (24; 25); G. Ickert (2); A. Ignatov (1); B. Jakobsson; (8); H.T. Johansson (23); B. Jonson (23); N. Kalantar-Nayestanaki (4); R.; Kanungo (18); A. Kelic-Heil (2); R. Kn\"obel (2); T. Kr\"oll (1); R.; Kr\"ucken (22); J. Kurcewicz (2); M. Labiche (26); C. Langer (6); T. Le Bleis; (22); R. Lemmon (26); O. Lepyoshkina (22); S. Lindberg (23); J. Machado (21),; J. Marganiec (3); V. Maroussov (27); J. Men\'endez (1; 3); M. Mostazo (5),; A. Movsesyan (1); A. Najafi (4); T. Nilsson (23); C. Nociforo (2); V. Panin; (1); A. Perea (11); S. Pietri (2); R. Plag (6); A. Prochazka (2); A. Rahaman; (15); G. Rastrepina (2); R. Reifarth (6); G. Ribeiro (11); M.V. Ricciardi; (2); C. Rigollet (4); K. Riisager (20); M. R\"oder (28; 9); D.M. Rossi; (2); J. Sanchez del Rio (11); D. Savran (3; 29); H. Scheit (1); A. Schwenk; (3; 1); H. Simon (2); O. Sorlin (12); V. Stoica (4; 30); B. Streicher; (4); J. Taylor (16); O. Tengblad (11); S. Terashima (2); R. Thies (23); Y.; Togano (3); E. Uberseder (31); J. Van de Walle (4); P. Velho (21); V. Volkov; (1); A. Wagner (9); F. Wamers (1); H. Weick (2); M. Weigand (6); C. Wheldon; (7); G. Wilson (32); C. Wimmer (6); J.S. Winfield (2); P. Woods (33); D.; Yakorev (9); M.V. Zhukov (23); A. Zilges (27); M. Zoric (2); K. Zuber (28),; R3B collaboration ((1) Institut f\"ur Kernphysik; Technische Universit\"at; Darmstadt; 64289 Darmstadt; Germany; (2) GSI Helmholtzzentrum f\"ur; Schwerionenforschung; D-64291 Darmstadt; Germany; (3) ExtreMe Matter; Institute EMMI; GSI Helmholtzzentrum f\"ur Schwerionenforschung GmbH; 64291; Darmstadt; Germany; (4) KVI; University of Groningen; Zernikelaan 25; NL-9747; AA Groningen; The Netherlands; (5) Departamento de F\'isica de Part\'iculas,; Universidade de Santiago de Compostela; 15706 Santiago de Compostela; Spain,; (6) Goethe-Universit\"at Frankfurt am Main; 60438 Frankfurt am Main; Germany,; (7) School of Physics; Astronomy; University of Birmingham; Birmingham B15; 2TT; United Kingdom; (8) Department of Physics; Lund University; S-22100; Lund; Sweden; (9) Helmholtz-Zentrum Dresden-Rossendorf; D-01328 Dresden,; Germany; (10) Department of Physics; Astronomy; Texas A\&M; University-Commerce; Commerce; Texas 75429; USA; (11) Instituto de Estructura; de la Materia; CSIC; Serrano 113 bis; E-28006 Madrid; Spain; (12) Grand; Acc\'el\'erateur National d'Ions Lourds (GANIL); CEA/DSM-CNRS/IN2P3; B.P.; 55027; F-14076 Caen Cedex 5; France; (13) University of Vigo; E-36310 Vigo,; Spain; (14) Department of Physics; University of Surrey; Guildford GU2 5FH,; United Kingdom; (15) Saha Institute of Nuclear Physics; 1/AF Bidhan Nagar,; Kolkata-700064; India; (16) Oliver Lodge Laboratory; University of Liverpool,; Liverpool L69 7ZE; United Kingdom; (17) Kurchatov Institute; Ru-123182; Moscow; Russia; (18) Astronomy; Physics Department; Saint Mary's; University; Halifax; NS B3H 3C3; Canada; (19) Facultad de Ciencias F\'isicas,; Universidad Complutense de Madrid; Avda. Complutense; E-28040 Madrid; Spain,; (20) Department of Physics; Astronomy; Aarhus University; DK-8000; {\AA}rhus C; Denmark; (21) Centro de Fisica Nuclear; University of Lisbon,; P-1649-003 Lisbon; Portugal; (22) Physik Department E12; Technische; Universit\"at M\"unchen; 85748 Garching; Germany; (23) Fundamental Fysik,; Chalmers Tekniska H\"ogskola; S-412 96 G\"oteborg; Sweden; (24) Department of; Physics; Astronomy; University of Tennessee; Knoxville; TN 37996; USA,; (25) Physics Division; Oak Ridge National Laboratory; P.O. Box 2008; Oak; Ridge; TN 37831; USA; (26) STFC Daresbury Laboratory; Daresbury; Warrington; WA4 4AD; United Kingdom; (27) Institut f\"ur Kernphysik; Universit\"at zu; K\"oln; D-50937 K\"oln; Germany; (28) Institut fur Kern- und Teilchenphysik,; Technische Universit\"at; 01069 Dresden; Germany; (29) Frankfurt Institut for; Advanced Studies FIAS; Frankfurt; Germany; (30) Department of Sociology /; ICS; University of Groningen; 9712 TG Groningen; The Netherlands; (31); Department of Physics; University of Notre Dame; Notre Dame; Indiana 46556,; USA; (32) Department of Physics; University of Surrey; Guildford GU2 5XH,; United Kingdom; (33) School of Physics; Astronomy; University of; Edinburgh; Edinburgh EH9 3JZ; United Kingdom)

arXiv:1209.0156·nucl-ex·August 15, 2019

Beyond the Neutron Drip-Line: The Unbound Oxygen Isotopes 25O and 26O

C. Caesar (1, 2), J. Simonis (1, 3), T. Adachi (4), Y. Aksyutina, (2, 3), J. Alcantara (5), S. Altstadt (6), H. Alvarez-Pol (5), N. Ashwood, (7), T. Aumann (1, 2), V. Avdeichikov (8), M. Barr (7), S. Beceiro (5), D., Bemmerer (9), J. Benlliure (5), C. A. Bertulani (10)

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TL;DR

This study combines experimental measurements and theoretical calculations to explore the properties of unbound neutron-rich oxygen isotopes 25O and 26O, revealing their energies, lifetimes, and excited states.

Contribution

It provides the first R3B-LAND experiment data on 25O and 26O, and compares findings with advanced shell-model calculations including residual three-nucleon forces.

Findings

01

25O ground state energy and lifetime determined

02

Upper limits for 26O ground state established

03

Evidence found for an excited state in 26O at around 4 MeV

Abstract

The very neutron-rich oxygen isotopes 25O and 26O are investigated experimentally and theoret- ically. In this first R3B-LAND experiment, the unbound states are populated at GSI via proton- knockout reactions from 26F and 27F at relativistic energies around 450 MeV/nucleon. From the kinematically complete measurement of the decay into 24O plus one or two neutrons, the 25O ground- state energy and lifetime are determined, and upper limits for the 26O ground state are extracted. In addition, the results provide evidence for an excited state in 26O at around 4 MeV. The ex- perimental findings are compared to theoretical shell-model calculations based on chiral two- and three-nucleon (3N) forces, including for the first time residual 3N forces, which are shown to be amplified as valence neutrons are added.

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