Physics Letters B (Apr 2022)
Investigating the predicted breathing-mode excitation of the Hoyle state
- K.C.W. Li,
- F.D. Smit,
- P. Adsley,
- R. Neveling,
- P. Papka,
- E. Nikolskii,
- J.W. Brümmer,
- L.M. Donaldson,
- M. Freer,
- M.N. Harakeh,
- F. Nemulodi,
- L. Pellegri,
- V. Pesudo,
- M. Wiedeking,
- E.Z. Buthelezi,
- V. Chudoba,
- S.V. Förtsch,
- P. Jones,
- M. Kamil,
- J.P. Mira,
- G.G. O'Neill,
- E. Sideras-Haddad,
- B. Singh,
- S. Siem,
- G.F. Steyn,
- J.A. Swartz,
- I.T. Usman,
- J.J. van Zyl
Affiliations
- K.C.W. Li
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; Department of Physics, University of Oslo, N-0316 Oslo, Norway; Department of Physics, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa; Corresponding author.
- F.D. Smit
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa
- P. Adsley
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA; Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA; School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa
- R. Neveling
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa
- P. Papka
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; Department of Physics, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa
- E. Nikolskii
- NRC Kurchatov Institute, RU-123182 Moscow, Russia; Flerov Laboratory of Nuclear Reactions, JINR, RU-141980 Dubna, Russia
- J.W. Brümmer
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; Department of Physics, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa
- L.M. Donaldson
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa
- M. Freer
- School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
- M.N. Harakeh
- Nuclear Energy Group, ESRIG, University of Groningen, 9747 AA Groningen, the Netherlands
- F. Nemulodi
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa
- L. Pellegri
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa
- V. Pesudo
- Department of Physics and Astronomy, University of the Western Cape, P/B X17, Bellville 7535, South Africa; Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Madrid 28040, Spain
- M. Wiedeking
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa
- E.Z. Buthelezi
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa
- V. Chudoba
- Flerov Laboratory of Nuclear Reactions, JINR, RU-141980 Dubna, Russia
- S.V. Förtsch
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa
- P. Jones
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa
- M. Kamil
- Department of Physics and Astronomy, University of the Western Cape, P/B X17, Bellville 7535, South Africa
- J.P. Mira
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa
- G.G. O'Neill
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; Department of Physics and Astronomy, University of the Western Cape, P/B X17, Bellville 7535, South Africa
- E. Sideras-Haddad
- School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa
- B. Singh
- Department of Physics and Astronomy, University of the Western Cape, P/B X17, Bellville 7535, South Africa
- S. Siem
- Department of Physics, University of Oslo, N-0316 Oslo, Norway
- G.F. Steyn
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa
- J.A. Swartz
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; Department of Physics, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa
- I.T. Usman
- iThemba LABS, National Research Foundation, PO Box 722, Somerset West 7129, South Africa; School of Physics, University of the Witwatersrand, Johannesburg 2050, South Africa
- J.J. van Zyl
- Department of Physics, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa
- Journal volume & issue
-
Vol. 827
p. 136928
Abstract
Knowledge of the low-lying monopole strength in C12—the Hoyle state in particular—is crucial for our understanding of both the astrophysically important 3α reaction and of α-particle clustering. Multiple theoretical models have predicted a breathing mode of the Hoyle State at Ex≈9 MeV, corresponding to a radial in-phase oscillation of the underlying α clusters. The C12(α,α′)C12 and C14(p,t)C12 reactions were employed to populate states in 12C in order to search for this predicted breathing mode. A self-consistent, simultaneous analysis of the inclusive spectra with R-matrix lineshapes, together with angular distributions of charged-particle decay, yielded clear evidence for excess monopole strength at Ex≈9 MeV which is highly collective. Reproduction of the experimentally observed inclusive yields using a fit, with consistent population ratios for the various broad states, required an additional source of monopole strength. The interpretation of this additional monopole resonance as the breathing-mode excitation of the Hoyle state would provide evidence supporting a D3h symmetry for the Hoyle state itself. The excess monopole strength may complicate analysis of the properties of the Hoyle state, modifying the temperature dependence of the 3α rate at T9≳2 and ultimately, the predicted nucleosynthesis in explosive stars.
