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Gull Lake October 2002
g-Spectroscopic Study of the r-Process
Waiting-Point Nuclide 130Cd
Iris Dillmann Mainz- Maryland- ANL- Oslo- CERN/
ISOLDE-Collaboration
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C.D. Coryell Chemists have been interested from
time immemorial in the chemical composition of
the world around us. (from The Chemistry of
Creation of the Heavy Elements, Journal of Chem.
Education, Vol. 38, No. 2, 1961)
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The N82 waiting points
130Cd the most important nucleus before breakout
of the N82 shell. Nuclear structure puzzles
in the 132Sn region!!!
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Target and Ionizer at CERN-ISOLDE
To the beamlines
Transfer line (Nb) 2200 K
UC2-C-Target
Primary beam 1 GeV protons, Intensity ca. 1013
p/ puls
Converter (Ta or W) ? n-induced spallation
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Laser setup at CERN-ISOLDE
BBO Barium-b-Borat-Kristall

• one Cu-vapor-laser as oscillator pumps the two
  others
• two dye-laser are pumped with 511 or 578 nm
• frequency-tripling by two BBO-cristals to get
  UV-radiation

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Selectivity
Three ways to separate Cd from isobars
1) Neutron- converter Suppression of
proton-rich isobaric spallation products
2) Chemical selectivity Laser ON
(laser-ionized Cd surface-ionized In) and
Laser OFF (only surface-ionized In)
3) HRS (High Resolution Separator) Mass
resolution M/DM 2 500 up to 10 000
CERN/ ISOLDE combines all three steps !
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Neutron- Converter

• 1 GeV-p-beam hits Ta- or W- rod 2 cm next to the
  target reaction-neutrons emitted from the
  converter n-induced spallation in the target
• proton-rich side of isobaric chain is suppressed
  in our case surface-ionized 130Cs

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RILIS Chemical selectivity

• 3-step laser ionization of Cd
• LIS-efficiency 10
• Selectivity 1000

Resonance Ionization Laser Ion Source
Ionization Potential 8.99 eV
578,2 nm
510,6 nm
5s5d 1D2
643,8 nm
5s5p 1P0
228,8 nm
5s2 1S0
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Mass Resolution
High Resolution Separator at CERN/ ISOLDE
DM/M up to 1/10 000 !!!
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Experimental g- data of the 130Cd decay
451 keV
315 keV
949 keV
1169 keV
Laser ON
Laser OFF
1669 keV
1735 keV
2120 keV
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130Cd decay scheme
Comparison with the OXBASH model (A. Brown)
(A) Prediction before experiment
(B) Post-calculation optimizing the
pn-interaction

• Important values
• one strongly fed Gamow-Teller-transition (0 ?
  1) (prediction QRPA)
• position of the 1-level (pg9/2?ng7/2)
• Qb-value (to be analyzed), but high value
  around 8.5 MeV expected

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Shell-model predictions for 130Cd b-decay
Calculation of log ft values for the 2QP 1 level
at 2.12 MeV
Martinez-Pinedo Langanke (Large -Scale
Shell-Model) Qb(Zuker) 7.56 MeV, T1/2 146
ms E(1) 1.55 MeV Ib 95 ? log ft 3.83
Moeller et al. (Quasi Particle Random Phase
Approximation) Qb(FRDM) 7.43 MeV, T1/2 663
ms E(1) 2.31 MeV Ib 63 ? log ft 4.38
Moeller et al. (QRPA incl. Folded-Yukawa,
Lipkin-Nogami) Qb(Audi) 8.5 MeV, T1/2 248
ms E(1) 2.31 MeV Ib 63 ? log ft 4.45
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Summary
Which log ft values needed to obtain exp. T1/2
(130Cd) of 162 ms?
LSSM (Qb(Zuker)) 7.56 MeV) log ft 3.83
? log ft too low
QRPA (Qb(FRDM)) 7.43 MeV) log ft 4.38
? T1/2 too long
QRPA (Qb(Audi)) 8.50 MeV) log ft 4.45
? We request a high Qb-value!
Experimentally known log ft for GT-transitions
involving ng7/2Äpg9/2 130In (1-) log ft
4.2 130In (10-) log ft 4.5 131In (9/2) log
ft 4.4 131In (21/2) log ft 4.5
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130Cd decay scheme
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Conclusions
The high energy of the ng7/2Äpg9/2 2QP 1 level
in 130In has added another nuclear structure
surprise in the 132Sn region
? Obviously shell structure around 132Sn82 not
yet fully understood ? further experiments at
CERN/ ISOLDE planned But the astrophysical
consequences are ? better understanding of
formation and r-process matter flow through the
A130 Nr, -peak
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Thanks
Karl-Ludwig Kratz (Kernchemie Mainz) William B.
Walters (University of Maryland) Andreas Wöhr
(Argonne National Laboratory/ UMD) Oliver Arndt,
Alex Brown (MSU), Per Hoff (Oslo), Kris Heyde
(Gent), Gabriel Martinez-Pinedo (Basel), Peter
Möller (LANL), Alexander N. Ostrowski, Bernd
Pfeiffer, Darek Seweryniak, Jason Shergur and the
CERN/ ISOLDE Collaboration
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How we REALLY measured the 130Cd decay
Darth Ka-El
An Exotic Particle