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

Sandrine CourtinSan Antonio May 29th, 2012

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

Sandrine Courtin

Institut Pluridisciplinaire Hubert Curien,and University of Strasbourg

France


Cluster bands → 16O(12C+), 18O(14C+), 20Ne(16O+), 44Ti(40Ca+)

→ Be and C neutron-rich isotopes with 2xn and 3xn configurations W. 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 MeV E2(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.

α clusters in light heavy-ionsα clusters in light heavy-ions


In the sd shell, based on 12C, 16O CN at high excitation energy, narrow resonances… Width = 100-200 keV, striking examples: 12C+12C and 12C+16O

12C+16O : collision at CB and below, low spin (0+-4+), Ex(28Si) ~ 25 MeV Radiative capture reaction 12C(16O,)28Si, gamma decay via ‘doorway’ states… cluster states, deformed

Heavier clusters


12C+16O breakup states in 28Si

Excitation energy (MeV)25

• 12C+16O ‘breakup’ states in 28Si up to E* = 45 MeV C.J. Metelko et al., J. Phys. G29 (2003), 697 • Reaction 12C(20Ne,12C16O)@ ANL

• Position Sensitive Double-Sided Silicon Strip Detectors for coincident particle detection

RC


Radiative Capture and heavy-ions

Nuclear astrophysics, light particles, inverse kinematics

Heavy-ionsHeavy-ions

GSI (J.G. Keller, K.H. Schmidt et al. PRC 29, 1569 (1984)) 90Zr(358 MeV)+90Zr -> 180Hg + σ= 40 pb More recently at Argonne (F. Camera et al., PLB 560, 155 (2003)) 89Y(352 MeV)+90Zr -> 179Au + Light heavy-ions: : 1212C+C+1212C -> C -> 2424Mg + Mg + Sandorfi et al. (Brookhaven) : Sandorfi et al. (Brookhaven) : large NaI detectorlarge NaI detector (~ 1980) (~ 1980) ResonancesResonances

EE > 18 MeV, decay to low-lying states of > 18 MeV, decay to low-lying states of 2424MgMgSame results for Same results for 1212C+C+1616O -> O -> 2828Si + Si +


To the 28Si prolate excited band

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), 155P.R. Christensen et al., Nucl.Phys. A 280 (1977) 189.

radiative capture resonances

To the 28Si ground state band

… … Capture Radiative and light heavy-ions / Decay studiesCapture Radiative and light heavy-ions / Decay studies1212C+C+1616O at 5 energiesO at 5 energies

CB

fusion

Ec.m. = 6.6, 7.2, 8.5, 8.8 and 9 MeV


First stageFirst stage

Second stageSecond stage

D.A

. H

utc

he

on

et

al.,

NIM

A 4

98

, 1

90

(2

00

3).

ISAC I : RNBs / Stable (OLIS) 0° spectrometer Tof : 21 m Beam rejection: 10Beam rejection: 101313

Acceptance : cone ½ angle 20 mrad

gaz/solid target focal plane (DSSSD, …) BGO ( = 50 % @ 5 MeV)

… … Capture Radiative and light heavy-ions/ Decay studies Capture Radiative and light heavy-ions/ Decay studies 1212C+C+1616OO


12C+16ORecoil spectrum vs ToF (28Si)

12C+16OGamma spectrum (28Si)2+ → 0+

4+ → 2+

3+,0+, 3-

~14 MeV

12C+16OHighest energy -ray

~14 MeV

25 MeV

~ 11 MeV

0 MeV28Si

S. Courtin et al., Fusion 06, San Servolo, AIP Conf. Proc. 853 (2006)

12C+16O/ Results


What is the structure of these states?What is the structure of these states?

28Si(12C-160) Ohkubo and Yamashita, Phys.Lett. B 578 (2004) 304.

→ → Links between cluster bands?Links between cluster bands?

… … Capture Radiative and light heavy-ions/ Decay studiesCapture Radiative and light heavy-ions/ Decay studies1212C+C+1212C and C and 1212C+C+1616OO

T. Ichikawa, Y. Kanada-En’yo and P. Möller, Phys. Rev. C 83 (2011)


simulation

experiment

19.3 MeV

p

n

24Mg

Resonance J = 0+,1-, 2+, 3-, 4+, 5-, 6+

28Si

20Ne

10 MeV

g.s.

25 MeV

Very well known sd shell nucleus

E0(MeV)

Co

un

ts

E0(MeV) 9.3 MeV

0+ only

Ex : J = 0+

12C+16O resonance spin ? / MC simulations


12C+16O / statistical vs structural effects

E = 8.5 MeV E = 9 MeV

D. Lebhertz, S. Courtin et al. Phys.Rev. C 85, 034333 (2012)

J = 5- (44%),6+ (56%) J = 5- (8%),6+ (86%) + stat. background

in good agreement with fusion resonance work(E. Schloemer et al. Phys. Rev. Lett. 51 (1983))


Direct feeding of 31- (deformed) at 6.9 MeV

3-1

25.3 MeV

6.9 MeV

28Sig.s.

E0(MeV)

E1(

MeV

)

Direct feeding of the 43+ (prolate) at 9.2 MeV

2+1

4+3

25.7 MeV

9.4 MeV

1.8 MeV

28Sig.s.

12C+16O / statistical vs structural effects

E = 9 MeVE = 8.5 MeV

E = 9 MeV


12C+16O below CB

A. Goasduff, PhD Thesis Université de Strasbourg 2012

E = 6.6 MeV, strong feeding of J= 1+,T=1 states

Decay scenario L = 1 transition from 0+, 1-, 2+ resonancecf 12C+12C, E = 6 MeV (D.G. Jenkins et al, Phys. Rev. C76 (2007))


12C+16O radiative capture cross-sections from our 2 experimental campaigns

12C+16O radiative capture cross-sections from our 2 experimental campaigns

D. Lebhertz, PhD Thesis University of Strasbourg, 2009

Larger cross-sections due to new decays paths

A. Goasduff, PhD Thesis University of Strasbourg, 2012


Future: radiative capture with the PARIS arrayFuture: radiative capture with the PARIS array

Experimental : Better resolution array (100 keV to 50 MeV), LaBr3 + NaI phoswichescoupled to a large acceptance spectrometer or used in a calorimeter mode

→ Individual peaks can be resolved

12C(12C,γ)24Mg, GEANT4 simulations for PARIS (200 LaBr3 spherical configuration)

12C+12C24Mgtoday

12C+12C24Mgtomorrow


this work

Metelko et al. data

ConclusionsConclusions

• Radiative capture reactions around CB 28Si(12C-16O), doorway states 11 MeV, (∼ +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’), (’), (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


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

CollaborationCollaboration

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

Documents

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