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Search for 28 Si cluster states through the 12 C+ 16 O radiative capture

Search for 28 Si cluster states through the 12 C+ 16 O radiative capture. Sandrine Courtin Institut Pluridisciplinaire Hubert Curien, and University of Strasbourg France. α clusters in light heavy-ions.

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Search for 28 Si cluster states through the 12 C+ 16 O radiative capture

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  1. Search for 28Si cluster states through the 12C+16O radiative capture Sandrine Courtin Institut Pluridisciplinaire Hubert Curien, and University of Strasbourg France

  2. α clusters in light heavy-ions • Cluster bands→ 16O(12C+a), 18O(14C+a), 20Ne(16O+a), 44Ti(40Ca+a) → Be and C neutron-rich isotopes with 2axn and 3axn configurationsW. Von Oertzen, HMI (dimers and polymers, Nucl.Phys. A734(2004))M. Freer, Charissa (Nucl.Phys. A738(2004)) • Stars examples of α clustering :→8Be(0+) Ex = 0.0 MeV→9Be(3/2-, 5/2-) Ex = 0.0, 2.43 MeVE2(5/2- → 3/2-) : 24 W.u. → 12C(0+) Ex = 7.65 MeV E2(0+ → 2+) : 8 W.u. → 16O(0+, 2+, 4+) Ex = 6.05, 6.92, 10.36 MeV (4p-4h)E2(2+ → 0+) : 27 W.u., E2(4+ → 2+) : 65 W.u.

  3. Heavier clusters • In the sd shell, based on 12C, 16OCN at high excitation energy, narrow resonances… Width = 100-200 keV, striking examples: 12C+12C and 12C+16O • 12C+16O : collisionat CB and below, low spin (0+-4+), Ex(28Si) ~ 25 MeV Radiative capture reaction 12C(16O, g)28Si, gamma decay via ‘doorway’ states… cluster states, deformed

  4. 25 Excitation energy (MeV) 12C+16O breakup states in 28Si RC • 12C+16O ‘breakup’ states in 28Si up to E* = 45 MeVC.J. Metelko et al., J. Phys. G29 (2003), 697 • Reaction 12C(20Ne,12C16O)a @ ANL • Position Sensitive Double-Sided Silicon Strip Detectors for coincident particle detection

  5. Radiative Capture and heavy-ions Nuclear astrophysics, light particles, inverse kinematics • Heavy-ions • GSI (J.G. Keller, K.H. Schmidt et al. PRC 29, 1569 (1984)) 90Zr(358 MeV)+90Zr -> 180Hg + g, σ= 40 pb More recently at Argonne (F. Camera et al., PLB 560, 155 (2003)) 89Y(352 MeV)+90Zr -> 179Au + g • Light heavy-ions: 12C+12C -> 24Mg + g Sandorfi et al. (Brookhaven) : large NaI detector (~ 1980) Resonances E > 18 MeV, decay to low-lying states of 24Mg Same results for 12C+16O -> 28Si + g

  6. … Capture Radiative and light heavy-ions / Decay studies 12C+16O at 5 energies radiative capture resonances fusion To the 28Si ground state band CB To the 28Si prolate excited band Ec.m. = 6.6, 7.2, 8.5, 8.8 and 9 MeV A.M. Sandorfi, in Treatise on Heavy-Ion Science, D.A. Bromley, Vol II, sec. 3. M.T. Collins, A.M. Sandorfi and D.H. Hoffmann, Phys.Rev. Lett. 49 (1982), 155 P.R. Christensen et al., Nucl.Phys. A 280 (1977) 189.

  7. … Capture Radiative and light heavy-ions/ Decay studies 12C+16O First stage Second stage D.A. Hutcheonet al., NIM A 498, 190 (2003). • ISAC I : RNBs / Stable (OLIS) • 0° spectrometer • Tof : 21 m • Beam rejection: 1013 • Acceptance : cone ½ angle 20 mrad • gaz/solid target • focal plane (DSSSD, …) • BGO (e = 50 % @ 5 MeV)

  8. 12C+16O/ Results 25 MeV ~ 11 MeV 0 MeV 28Si 12C+16O Gamma spectrum (28Si) 2+→ 0+ ~14 MeV 4+→ 2+ 3+,0+, 3- 12C+16O Recoil spectrum vs ToF (28Si) 12C+16O Highest energy -ray ~14 MeV S. Courtin et al., Fusion 06, San Servolo, AIP Conf. Proc. 853 (2006)

  9. … Capture Radiative and light heavy-ions/ Decay studies 12C+12C and 12C+16O What is the structure of these states? T. Ichikawa, Y. Kanada-En’yo and P. Möller, Phys. Rev. C 83 (2011) 28Si(12C-160)Ohkubo and Yamashita, Phys.Lett. B 578 (2004) 304. → Links between cluster bands?

  10. 12C+16O resonance spin ? / MC simulations 0+ only Resonance Jp = 0+,1-, 2+, 3-, 4+, 5-, 6+ Ex : Jp = 0+ 25 MeV aa n 19.3 MeV p 20Ne a 9.3 MeV E0(MeV) 10 MeV simulation 24Mg experiment Counts g.s. 28Si Very well known sd shell nucleus E0(MeV)

  11. 12C+16O / statistical vs structural effects E = 8.5 MeV E = 9 MeV JP = 5- (44%),6+ (56%) JP = 5- (8%),6+ (86%) + stat. background in good agreement with fusion resonance work(E. Schloemer et al. Phys. Rev. Lett. 51 (1983)) D. Lebhertz, S. Courtin et al. Phys.Rev. C 85, 034333 (2012)

  12. E1(MeV) E0(MeV) 25.3 MeV 25.7 MeV 4+3 9.4 MeV 3-1 6.9 MeV 1.8 MeV 2+1 g.s. g.s. 28Si 28Si 12C+16O / statistical vs structural effects E = 8.5 MeV E = 9 MeV Direct feeding of the 43+ (prolate) at 9.2 MeV Direct feeding of 31- (deformed) at 6.9 MeV E = 9 MeV

  13. 12C+16O below CB E = 6.6 MeV, strong feeding of JP= 1+,T=1 states Decay scenario L = 1 transition from 0+, 1-, 2+resonance cf 12C+12C, E = 6 MeV (D.G. Jenkins et al, Phys. Rev. C76 (2007)) A. Goasduff, PhD Thesis Université de Strasbourg 2012

  14. 12C+16O radiative capture cross-sections from our 2 experimental campaigns Larger cross-sections due to new decays paths D. Lebhertz, PhD Thesis University of Strasbourg, 2009 A. Goasduff, PhD Thesis University of Strasbourg, 2012

  15. Future: radiative capture with the PARIS array Experimental : Better resolution g array (100 keV to 50 MeV), LaBr3 + NaI phoswichescoupled to a large acceptance spectrometer or used in a calorimeter mode 12C+12C24Mg tomorrow 12C+12C24Mg today 12C(12C,γ)24Mg, GEANT4 simulations for PARIS (200 LaBr3 spherical configuration) → Individual peaks can be resolved

  16. Conclusions • Radiative capture reactions around CB • 28Si(12C-16O), doorway states ∼11 MeV, (α+24Mg = 9.99 MeV) • ➜ impact on the capture cross-section • Results compared to simulations • above CB, 5-, 6+ spins for the resonance and feeding of specific states • below CB, large feeding of 1+, T = 1 states (11.45 MeV),like in 24Mg (10.70 MeV). Isovector M1 transitions, spin-flip excitations give rise to 1+,T=1 states in the N=Z nuclei 24Mg and 28Si (same states strongly observed in (e,e’), (g,g’), (p, p’), (p,n)).2+ resonance for 28Si and 24Mgin C+C, it is proposed that the resonance is connected with the 24Mg ISGQR (on 24Mg g.s.)in C+O, the 2+ resonant state could be connected with the 28Si  ISGQR built on the prolate structure (~ 7MeV). Just N=Z selection rule ? • Decay scenarios will be confirmed with better resolution data with the PARIS detector Metelko et al. data this work

  17. Collaboration S.Courtin, A. Goasduff, D. Lebhertz, A. Michalon, F. Haas et al., Department of Subatomic Research, IPHC, Strasbourg, France D.G. Jenkins, P.A. Marley et al., Physics Department, University of York, UK D.A Hutcheon, C. Ruiz, J. Fallis et al., TRIUMF, Vancouver, Canada

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