Decay Modes of Narrow Molecular ResonancesDecay Modes of Narrow Molecular ResonancesDecay Modes of Narrow Molecular Resonances

Sandrine Courtin, Fusion 06, San Servolo, March 2006

Sandrine CourtinSandrine CourtinInstitut Pluridisciplinaire Hubert Curien, Institut Pluridisciplinaire Hubert Curien,

UniversitUniversitéé Louis Pasteur, Strasbourg, FranceLouis Pasteur, Strasbourg, France

1. Resonances in light heavy-ion collisions1. Resonances in light heavy1. Resonances in light heavy--ion collisionsion collisions

2. Resonant Radiactive CaptureReactions for 12C+12C and 12C+16O

2. Resonant Radiactive Capture2. Resonant Radiactive CaptureReactions for Reactions for 1212C+C+1212C and C and 1212C+C+1616OO

3. Results3. Results3. Results

Sandrine Courtin, Fusion 06, San Servolo, March 2006

Resonances in light heavyResonances in light heavy--ionsions

Known for more than 30 years

Resonances Resonances ?? molecular states ?molecular states ?narrow resonancesnarrow resonances

24Mg+24Mg, Γ ~ 150 keV, EB = 2 x CB, high spin (36+)

M.M.--D. Salsac’s D. Salsac’s talktalk

12C+12C, Γ = 150 keV, EB ~ CB, low spin (0-4) 12C+16O, Γ = 150 keV, EB ~ CB, low spin (0-4)

Decay modesDecay modes

Fragment andFragment andparticle decayparticle decay

γγ decaydecay

Sandrine Courtin, Fusion 06, San Servolo, March 2006

Radiative Capture and HeavyRadiative Capture and Heavy--IonsIons

Nuclear Astrophysics, light particlesInverse kinematics

Heavy Ions, a few systems only …Heavy Ions, a few systems only …

§§ Pioneering study at GSI (J.G. Keller, K.H. Schmidt et al. PRC 29, 1569 (1984)) 90Zr(358 MeV)+90Zr -> 180Hg + xγ σ = 40 pbRecently at Argonne (F. Camera et al., PLB 560, 155 (2003))89Y(352 MeV)+90Zr -> 179Au + xγ

§ Light heavyLight heavy--ions : ions : 1212C+C+1212C C --> > 2424Mg + Mg + γγSandorfi et al. (Brookhaven) :Sandorfi et al. (Brookhaven) : NaINaI (~ 1980)(~ 1980)

ResonancesResonancesEEγγ > 18 MeV, deexcitation to the low> 18 MeV, deexcitation to the low--lying states of lying states of 2424MgMgSimilar results for Similar results for 1212C+C+1616O O --> > 2828Si + Si + γ (1981)γ (1981)

Sandrine Courtin, Fusion 06, San Servolo, March 2006

… … Radiative Capture and light HeavyRadiative Capture and light Heavy--Ions / Decay StudiesIons / Decay Studies1212C+C+1212C and C and 1212C+C+1616OO

Jenkins et al. 12C(12C,γ)24Mg, more recently :Gammasphere (Berkeley) as a calorimeter:

Decay of resonances not statistical, feeding of Kπ = 2+ bandFeeding of states ~ 10 MeVFeeding of states ~ 10 MeV (24Mg shape isomers with 12C-12C structure ?)

FMA (Argonne) no γ detection :Due to new decay channels : larger radiative capture cross-sections

D.G. Jenkins et al., PRC 71, 041301(R)(2005)

What is the structure of those states ?What is the structure of those states ?

- Model predictions of 16O+12C cluster bands in 28Si from

Ohkubo and Yamashita, Phys.Lett. B 578 (2004) 304.

?? Links between lowLinks between low--lying members of these cluster bands ?lying members of these cluster bands ?

-Predictions for 12C+12C P. Descouvemont and D. BayePhys.Lett. 169 B (1986) 143

Sandrine Courtin, Fusion 06, San Servolo, March 2006

1212C+C+1212C and C and 1212C+C+1616O experimental studiesO experimental studies

To the prolate excited band

M.T. Collins, A.M. Sandorfi and D.H. Hoffmann, Phys.Rev. Lett. 4 9 (1982), 1553 / A.M. Nathan, A.M. Sandorfi and T.J. Bowles, Phys.Rev. C24 (1981) 931.

12C(16O,γ)28Si

To the ground state band

12C(12C,γ)24Mg

To the ground state

To the first 2+

To the 4+ and 2nd 2+

A.M. Sandorfi, in Treatise on Heavy-Ion Science, D.A. Bromley, Vol II, sec. 3.

1212C+C+1212C and C and 1212C+C+1616O experimental studiesO experimental studies

Sandrine Courtin, Fusion 06, San Servolo, March 2006

1212C+C+1212C(12.0, 13.4, 16.0 MeV ONC(12.0, 13.4, 16.0 MeV ON--resonance) at DRAGONresonance) at DRAGON (Triumf, D.G. Jenkins et al., March 2004)(Triumf, D.G. Jenkins et al., March 2004)1212C+C+1616O(20.7 MeV ONO(20.7 MeV ON--resonance) at DRAGONresonance) at DRAGON (Triumf, S. Courtin et al., August 2005)(Triumf, S. Courtin et al., August 2005)Solid enriched 12C targets (40 µg/cm2)Energies ON/OFF resonanceDRAGON + BGO arrayWhat is the decay of the resonances ?Is there a multistep decay feeding doorway cluster 24Mg,28Si states ?

++

Hyper deformed

‘Multi-step’GDR

24Mg,28Si

20-25 MeV

Super deformed 24Mg,28Si

Competition between

1212C+C+1212C and C and 1212C+C+1616O experimental studiesO experimental studies

Sandrine Courtin, Fusion 06, San Servolo, March 2006

First StageFirst Stage

Second StageSecond Stage

D.A

.Hu

tch

eon

et a

l., N

IM A

498

, 190

(200

3).

§ ISAC I : RNBs / Stable (OLIS)§ 0° spectrometer§ Tof on 17 m§ Beam rejection 10Beam rejection 101313

§§ Acceptance : cone ½ angle 20 mrad

§ gas/solid target system§ recoil detectors (DSSSD, …)§ BGO array (ε = 50 % @ 5 MeV)

1212C+C+1616O and O and 1212C+C+1212C, results of the Dragon experimentC, results of the Dragon experiment

Sandrine Courtin, Fusion 06, San Servolo, March 2006

12C+16ORecoil spectrum (28Si)

12C+16OGamma spectrum (28Si)2+ ? 0+

4+ ? 2+

3+,0+, 3-

~13 MeV

12C+16OHighest energy γ-ray

~13 MeV

26 MeV

~ 13 MeV

0 MeV28Si

20 MeV

~ 10 MeV

0 MeV24Mg

12C+12C~ 10 MeV

MonteMonte--Carlo simulations, Carlo simulations, 1212C+C+1212CC

Sandrine Courtin, Fusion 06, San Servolo, March 2006

GEANT 3 simulations of the 12C+12C reaction as a first stepGEANT 3 simulations of the 12C+12C reaction as a first step

20 MeV

~ 10 MeV

0 MeV24Mg

2+

2+

0+

Angular distributions

Branching ratio ?Branching ratio ?

Conclusions, future plansConclusions, future plansConclusions, future plans

Sandrine Courtin, Fusion 06, San Servolo, March 2006

Multistep decay of resonances dominant for both systems 24Mg(12C-12C), states around 10 MeV, (α+20Ne threshold = 9.32 MeV)28Si(12C-16O), states around 13 MeV, (α+24Mg threshold = 9.99 MeV)

What are those states ? There are candidates in the litterature, i.e. unbound low spin states with Γγ/Γ ~ 1Simulations of different scenarii under progress

A definitive answer concerning the identification of the doorway statesAn experiment accepted at ANL (FMA + Gammasphere)1 system (12C+12C) at 1 energy (6 MeV resonance)

It would be nice to have a new spectrometer with a higher acceptIt would be nice to have a new spectrometer with a higher acceptance than Dragonance than Dragonand a and a γγ--array with high efficiency and a resolution of array with high efficiency and a resolution of ~~11--2 2 % (array of LaBr% (array of LaBr33(Ce))(Ce))

We are on the way to clearly identify EM transitions between cluster states ! We are on the way to clearly identify EM transitions between cluWe are on the way to clearly identify EM transitions between cluster states ! ster states !

Sandrine Courtin, Fusion 06, San Servolo, March 2006Sandrine Courtin, Fusion 06, San Servolo, March 2006

Collaboration :

S. Courtin, F. Haas, M.-D. Salsac, A. Michalon, P. Papka, C. Beck, M. Rousseau, A. Sanchez I Zafra

IPHC, Strasbourg, France

D.G. Jenkins, B.R. Fulton, R.G. Glover, P.E. KentUniversity of York, United-Kingdom

C.J. ListerArgonne National Laboratory, USA

D.A. Hutcheon, C. Davis, J.E. Pearson and the DRAGON collaborationTriumf, Vancouver, Canada

ThanksThanks !!