 -Spectroscopic Study of the r-Process Waiting-Point Nuclide 130 Cd Iris Dillmann Mainz- Maryland- ANL- Oslo- CERN/ ISOLDE-Collaboration Gull Lake October 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 points 130 Cd: the most important nucleus before breakout of the N=82 shell. Nuclear structure „puzzles“ in the 132 Sn region!!!

Target and Ionizer at CERN-ISOLDE Primary beam: 1 GeV protons, Intensity: ca p/ puls Converter (Ta or W)  n-induced spallation UC 2 -C- Target Transfer line (Nb) ~2200 K To the beamlines

Laser 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

Selectivity 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~ up to CERN/ ISOLDE combines all three steps !

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 130 Cs

Resonance Ionization Laser Ion Source RILIS: Chemical selectivity Ionization Potential: 8.99 eV 510,6 nm 578,2 nm 643,8 nm 228,8 nm 5s5d 1 D 2 5s5p 1 P 0 5s 2 1 S 0 3-step laser ionization of Cd LIS-efficiency:  10% Selectivity:  1000

Mass Resolution High Resolution Separator at CERN/ ISOLDE  M/M up to 1/ !!!

Experimental  - data of the 130 Cd decay 315 keV 451 keV 949 keV 1169 keV 2120 keV 1669 keV 1735 keV Laser ON Laser OFF

130 Cd decay scheme (A) Prediction before experiment (B) Post-calculation: optimizing the  -interaction Important values Important values: one strongly fed Gamow- Teller-transition (0 +  1 + ) (prediction QRPA) position of the 1 + -level (  g 9/2  g 7/2 ) Q  -value (to be analyzed), but „high“ value around 8.5 MeV expected Comparison with the OXBASH model (A. Brown)

Shell-model predictions for 130 Cd  -decay Moeller et al. (Quasi Particle Random Phase Approximation) Q  (FRDM)= 7.43 MeV, T 1/2 = 663 ms E(1+)= 2.31 MeV I  = 63%  log ft = 4.38 Moeller et al. (QRPA incl. Folded-Yukawa, Lipkin-Nogami) Q  (Audi)= 8.5 MeV, T 1/2 = 248 ms E(1+)= 2.31 MeV I  = 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, T 1/2 = 146 ms E(1+)= 1.55 MeV I  = 95%  log ft = 3.83

Experimentally known log ft for GT-transitions involving g 7/2  g 9/2 130 In (1 - ): log ft= In (10 - ):log ft= In (9/2 + ):log ft= In (21/2 + ):log ft= 4.5 Which log ft values needed to obtain exp. T 1/2 ( 130 Cd) of 162 ms? Summary LSSM (Q  (Zuker))= 7.56 MeV): log ft= 3.83 QRPA (Q  (FRDM))= 7.43 MeV): log ft= 4.38 QRPA (Q  (Audi))= 8.50 MeV): log ft= 4.45  log ft too low  T 1/2 too long  We request a high Q  -value!

130 Cd decay scheme

Other „surprises“: low p 3/2, p 1/2 SP neutron states in 133 Sn 83 trend of low 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 T 1/2 and P n values of 131 Cd 83 low  d 5/2 SP proton state in 135 SbConclusions The high energy of the [ g 7/2  g 9/2 ] 2QP 1 + level in 130 In has added another „nuclear structure surprise“ in the 132 Sn region  Obviously shell structure around 132 Sn 82 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 A  130 N r,  -peak

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

How we REALLY measured the 130 Cd decay Darth Ka-El An Exotic Particle