Negative-parity%20structures%20in%20fission%20fragments

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Negative-parity structures in fission fragments
1 Ci CARIBU Yield

• Wm. David Kulp, III
• Georgia Institute of Technology
• ATLAS Users workshop
• 8 August 2009

105/s
104/s
103/s
NS3 onset of collectivity NE of 132Sn NS9
evolution of octupole collectivity p d5/2,
h11/2 ? f7/2, i13/2 near Fermi surface
E(1-)
146Ce
148Ba
150Nd
A
2
Systematic studies of the low-energy octupole
bands in the neutron rich N90 nuclei are needed.
The region has the second-lowest known octupole
degree of freedom.
146Ba, 148Ce bands elucidated through prompt
fission ? decay.

• What is the nature of these collective
  structures? Vibrational? Stable octupole
  deformation? Clusters? Tetrahedral?

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Multiple octupole bands strongly populated in
multi-Coulex.
b
a
Sensitivity will not be as high with CARIBU the
152Sm experiment had 2x1010 particles/sec. The
lack of experimental results in the rare earth
region of interest should ... stand as a
challenge to experimentalists. In particular, it
would be of great interest to identify the Kp0
and 0- bands to high spin in 144Ba, 146Ba, 148Ce,
148Nd, 150Nd, 152Sm, 152Gd, 154Gd, and
156Dy. Sheline and Sood, Phys. Rev. C 34, 2362
(1986).
b
a
5
Systematics indicate the minimum for coexisting
K0- bands occurs in 148Ce and 150Nd.

• Gammasphere (or GRETINA) CHICO (CARIBU)
  these structures are accessible through
  multiple-step Coulomb excitation.

6
Results of extensive studies on 110-116Cd

• Vibrational interpretation breaks down at
  3-phonon level, systematically NO suitable
  candidates for 0, 2 members
• 0 levels only possible collective transitions
  observed are to 2 intruder level
• 2 level only collective decays to 0 2-phonon
• Are the Cd nuclei really vibrational?
• If the Cd are not vibrational, what are they?
• Fundamental question If our paradigms arent
  vibrators, what does this imply about the
  existence of vibrations in nuclei?

X X
3h?2
0,2,3,4,6
2h?2
0,2,4
h?2
2
0
0
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Programme of Coulex and ß-decay studies

• Goal to understand the evolution of structure
  from valley of stability to neutron rich
• Extensive data on 110-116Cd nuclei suggest a
  breakdown of vibrational motion at low-spins
• Presence of low-lying intruder states complicates
  structure
• Is a vibrational description the best model for
  heavier Cd isotopes?
• Do the Pd and Ru nuclei behave as spherical
  vibrators, and how do their structure evolve away
  from stability?

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Programme of Coulex and ß-decay studies

• Test rotational description of stable Cd nuclei
  to high spin
• Digital GS with CHICO makes available
  high-quality data in 1d of beam time
  systematic studies over an isotope chain in 1
  week!
• Nuclei like stable Cd make for an ideal test
  cases due to large amounts of complementary data
  to constrain Coulex analysis

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Programme of Coulex and ß-decay studies

• Study structure of neutron rich Pd isotopes via
  ß-decay of heavy Rh
• refactory element, extremely challenging/impossibl
  e at ISOL facilities
• For high-intensity beams desirable to have LEBT
  to GS to enable vital angular correlation studies
  

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Programme of Coulex and ß-decay studies

• Study structure of neutron rich Ru isotopes via
  Coulex and ß-decay of heavy Tc
• refactory element, extremely challenging/impossibl
  e at ISOL facilities
• For high-intensity beams desirable to have LEBT
  to GS to enable vital angular correlation studies