-Spectroscopic Study -Spectroscopic Study of the r-Process of the r-Process

Waiting-Point Nuclide Waiting-Point Nuclide 130130CdCd

Iris DillmannMainz- Maryland- ANL- Oslo-CERN/ ISOLDE-Collaboration

Gull LakeGull LakeOctober 2002October 2002

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)

The N=82 waiting pointsThe N=82 waiting points

130Cd: the mostimportant nucleusbefore breakout of the N=82 shell.

Nuclear structure „puzzles“ in the 132Sn region!!!

Target and Ionizer at CERN-ISOLDETarget and Ionizer at CERN-ISOLDE

Primary beam:Primary beam:1 GeV protons, 1 GeV protons,

Intensity: ca. 10Intensity: ca. 101313 p/ puls p/ puls

Converter (Ta or W) n-induced spallation

UC2-C-Target

Transfer line (Nb)~2200 K

To the beamlines

Laser setup at CERN-ISOLDELaser setup at CERN-ISOLDE

BBO: Barium--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

SelectivitySelectivity

Three ways to separate Cd from isobars:

2) Chemical selectivity: Laser ON (laser-ionized Cd + surface-ionized In) and Laser OFF (only surface-ionized In)

1) Neutron- converter:Suppression of proton-rich isobaric spallation products

3) HRS (High Resolution Separator): Mass resolution M/M~ 2 500 up to 10 000

CERN/ ISOLDE combines all three steps !

Neutron- ConverterNeutron- 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

ResonanceIonizationLaserIonSource

RILIS: Chemical selectivityRILIS: Chemical selectivity

Ionization Potential:8.99 eV

510,6 nm510,6 nm578,2 nm578,2 nm

643,8 nm643,8 nm

228,8 nm228,8 nm

5s5d 1D2

5s5p 1P0

5s2 1S0

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

Mass ResolutionMass Resolution

HighResolutionSeparatorat CERN/ ISOLDE

M/M up to 1/10 000 !!!

Experimental Experimental - data of the - data of the 130130Cd decayCd decay

315 keV 451 keV949 keV

1169 keV

2120 keV

1669 keV

1735 keV

Laser ON

Laser OFF

130130Cd decay schemeCd decay scheme

(A) Prediction before experiment

(B) Post-calculation: optimizing the -interaction

Important valuesImportant values: • one strongly fed Gamow-Teller-transition (0+ 1+) (prediction QRPA)

• position of the 1+-level (g9/2g7/2)

• Q-value (to be analyzed), but „high“ value around 8.5 MeV expected

Comparison with the OXBASH model

(A. Brown)

Shell-model predictions forShell-model predictions for 130 130Cd Cd -decay-decay

Moeller et al. (Quasi Particle Random Phase Approximation)Q(FRDM)= 7.43 MeV, T1/2= 663 msE(1+)= 2.31 MeVI= 63% log ft = 4.38

Moeller et al. (QRPA incl. Folded-Yukawa, Lipkin-Nogami)Q(Audi)= 8.5 MeV, T1/2= 248 msE(1+)= 2.31 MeVI= 63% log ft = 4.45

Calculation of log ft values for the 2QP 1+ level at 2.12 MeV

Martinez-Pinedo & Langanke (Large -Scale Shell-Model)Q(Zuker)= 7.56 MeV, T1/2= 146 msE(1+)= 1.55 MeVI= 95% log ft = 3.83

Experimentally known log ft for GT-transitions involving g7/2g9/2

130In (1-): log ft= 4.2130In (10-): log ft= 4.5131In (9/2+): log ft= 4.4131In (21/2+): log ft= 4.5

Which log ft values needed to obtain exp. T1/2 (130Cd) of 162 ms?

SummarySummary

LSSM (Q(Zuker))= 7.56 MeV):log ft= 3.83QRPA (Q(FRDM))= 7.43 MeV):log ft= 4.38QRPA (Q(Audi))= 8.50 MeV):log ft= 4.45

log ft too low

T1/2 too long

We request a high Q-value!

130130Cd decay schemeCd decay scheme

Other „surprises“:

• low p3/2, p1/2 SP neutron states in 133Sn83

• trend of low 21+ states and „high“ B(E2) values

in neutron-rich Cd Isotopes up to N=80

• trend of high Q values of neutron-rich Cd nuclides

• very low T1/2 and Pn values of 131Cd83

• low d5/2 SP proton state in 135Sb

ConclusionsConclusionsThe high energy of the [g7/2g9/2] 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

ThanksThanks

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

How we REALLY measured the How we REALLY measured the 130130Cd decayCd decay

Darth Ka-ElDarth Ka-El

An Exotic An Exotic ParticleParticle