Slajd 1

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Adam Maj IFJ PAN Krakow
Search for Pigmy Dipole Resonance in
68Ni RISING experiment in GSI
EWON Meeting Prague, 10-12 May, 2007
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RISING Rare ISotope INvestigation at GSI

• The Accelerators
• UNILAC (injector) Elt11.5 MeV/n
• SIS 18Tm corr. U 1 GeV/n
• Beam Currents 108 - 109 pps

• FRS --gt secondary radioactive ion beams
• Fragmentation or fission of primary beams
• High secondary beam energies
• 100 700 MeV/u
• Fully stripped ions
• Reactions on a secondary target
• Implantation inside a stopper

• Nuclear structure of exotic nuclei studied by
  Secondary fragmentation and Relativistic Coulomb
  excitation
• g-factor measurements
• Isomeric gamma and beta decay studies

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EUROBALL Cluster Detectors Beam
Tracking system
Why at FRS_at_GSI ?

• Unique European facility for relativistic (b
  0.4) exotic beams
• lifetime range 100 ns
• fully stripped beams
• Spin Aligned beams

Miniball Hector
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EUROBALL Cluster Detectors Beam
Tracking system
Miniball Hector
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EUROBALL Cluster Detectors Miniball HPGe
segmented detectors
HECTOR Large 14.5 x 17 cm BaF2 Detectors
CATE E-DE telescope event by event beam
identification
Coulomb Excitation at Relativistic Energy

• Relativistic Coulomb excitation of nuclei near
  100Sn
• New Shell structure at NgtgtZ
• Mirror symmetry of new (sub)shell closures 36S
  36Ca
• Triaxiality in even-even core nuclei of N75
  isotones
• E1 Collectivity in neutron rich nuclei 68Ni

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Cross-section for electromagnetic excitations
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GDR and PDR
N
Average Transition charge densities
P
Richter NPA 731(2004)59
Richter NPA 731(2004)59
Average Transition charge densities
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g-decay of the Giant and Pigmy Dipole
Resonaces Excited via relativistic Coulomb
Excitation
PDR have large impact on understanding of the
r-process nucleosynthesis (S. Goriely. Phys.
Lett. B436 (1998) 1)
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Question How collective properties changes
moving to neutron rich nuclei?
Dipole strength shifts at low energy Collective
or non-collective nature of the
transitions? Stable nuclei ? photoabsorption Ex
otic nuclei Virtual photon breakup LAND
experiment Virtual photon scattering RISING
experiment
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Coulomb excitation of 68Ni (600 MeV A)
Outgoing 68Ni
E (CsI)
1.2
4.4
DE (Si)
6 Days of effective beam time 400 GB of data
recorded 3 107 good 68Ni events recorded
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Coulomb excitation of 68Ni (600 MeV A) Pygmy
Dipole Resonance ?
Preliminary
Preliminary
Preliminary
Red lines GEANT4 simulation assuming 10.8 MeV
monoenergetic transition
A structure appears at 10-11 MeV in all detector
types
A. Bracco et al., Acta Phys. Pol. B38, 1229
(2007), F. Camera et al., to be published
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CONCLUSIONS
RMF
RPA
68Ni
68Ni
10 MeV
10 MeV
G. Colo private communications
D. Vretnar et al. NPA 692(2001)496

• Both RPA and RMF approaches predict for 68Ni
  Pygmy strength at approximately 10.8 MeV for 68Ni
  
• The degree of collectivity is still debated

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COLLABORATION Milano A. Bracco, F. Camera, O.
Wieland, G. Benzoni, S. Leoni, B.
Million, Kraków P. Bednarczyk, J. Grebosz, M.
Kmiecik, A. Maj, K. Mazurek, W. Meczynski, J.
Styczen GSI T. Aumann, H.J. Wollersheim, J.
Gerl, I. Kojouharow,. Legnaro G. de Angelis,
A. Gadea, D. Napoli,.. Sofia/Camerino D.
Balabanski