1. 1 Decay studies of r-process nuclei Karl-Ludwig Kratz - Max-Planck-Institut für Chemie, Mainz, Germany - Department of Physics, Univ. of Notre Dame, USA T 1/2 PnPn SnSn nn  HRIBF 2006

2. 2 scaled theoretical solar r-process scaled solar r-process Nb Zr Y Sr Mo Ru Rh Pd Ag Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Os Ir Pt Au Pb Th U Ga Ge Cd Sn Elemental abundances in UMP halo stars r-process observables Solar system isotopic abundances, N r,  “FUN-anomalies” in meteoritic samples isotopic composition Ca, Ti, Cr, Zr, Mo, Ru, Nd, Sm, Dy ↷ r-enhanced Historically, nuclear astrophysics has always been concerned with interpretation of the origin of the chemical elements from astrophysical and cosmochemical observations description in terms of specific nucleosynthesis processes (already B²FH, 1957).  [‰] ALLENDE INCLUSION EK-1-4-1 Mass number CS 22892-052 abundances T 9 =1.35; n n =10 20 - 10 28 R-process observables, Bi

3. 3 Nuclear-data needs for the classical r-process  nuclear masses S n -values  r-process path Q , S n -values  theoretical  -decay properties, n-capture rates   -decay properties  neutron capture rates  fission modes T 1/2  r-process progenitor abundances, N r,prog P n  smoothing N r,prog N r,final (N r,  )  RC +  DC  smoothing N r,prog during freeze-out SF,  df, n- and -induced fission  “fission (re-) cycling”; r-chronometers  -decay freeze-out  nuclear structure development - level systematics - “understanding”  -decay properties - short-range extrapolation into unknown regions

4. 4 History and progress in measuring r -process nuclei Definition: r-process isotopes lying in the process path at freeze-out ↷ when r-process falls out of (n,  )-( ,n) equilibrium even-neutron isotopes ↷ “waiting points” important nuclear-physics property T 1/2 odd-neutron isotopes ↷ connecting the waiting points important nuclear-physics property S n   n.  In 1986 a new r-process astrophysics era started: at the ISOL facilities OSIRIS, TRISTAN and SC-ISOLDE T 1/2 of N=50 “waiting-point” isotope 80 Zn 50 (top of A  80 N r,  peak; “weak” r-process) T 1/2 of N=82 “waiting-point” isotope 130 Cd 82 (top of A  130 N r,  peak; “main” r-process) In 2006, altogether more than 50 r-process nuclei have been measured, which lie in the process path at freeze-out. These r-process isotopes range from 68 Fe to 139 Sb. The large majority of these exotic nuclei was identified at CERN/ISOLDE via the decay mode of  –delayed neutron emission.

5. 5 What we knew already in 1986... K.-L. Kratz et al (Z. Physik A325; 1986) Exp. at old SC-ISOLDE with plasma ion-source quartz transfer line and  dn counting Problems: high background from -surface ionized 130 In, 130 Cs -molecular ions [ 40 Ca 90 Br] + Request: SELECTIVITY ! Shell-model (QRPA; Nilsson/BCS) prediction 1.0 T 1/2 (GT) = 0.3 s 4.1 1+1+ 2.0 g 7/2,  g 9/2 Q  = 8.0 MeV 1+1+ 1+1+ 1+1+ 1+1+ 1+1+ 1+1+ 1+1+ 0 1.0 3.0 4.0 5.0 6.0 1-1- IKMz – 155R(1986) T 1/2 = 230 ms T 1/2 = (195 ± 35) ms

6. 6 The r-process “waiting-point“ nucleus 130 Cd QQ 7.0 8.9 2.9 2QP 4QP J  =1 + { g 7/2,  g 9/2 } SnSn T 1/2, Q , E(1 + ), I  (1 + ), log ft 1.2...obtain a physically consistent picture! “free choice” of combinations : low E(1 + ) with low Q  high E(1 + ) with low Q  low E(1 + ) with high Q  high E(1 + ) with high Q  T 1/2 (GT) 233 ms 1130 ms 76 ms 246 ms (log ft=4.1)

7. 7 Ag CdIn Cs Sn SbTeIXe Improvements since 1993 at PS-Booster ISOLDE Fast UC x target Neutron converter Laser ion-source Hyperfine splitting Isobar separation Repeller Chemical separation Multi-coincidence setup Request: Selectivity ! 50 800 >10 5 the Ag “needle” in the Cs “haystack” Why ? How?

8. 8 Request: Selectivity ! Laser ion-source (RILIS) Chemically selective, three-step laser ionisation of Cd into continuum 130 Cd 1669 keV 130 Cd 1732 keV Laser ON Laser OFF 130 Sb 1749 keV Energy [keV]  -singles spectrum Laser ON Laser OFF Comparison of Laser ON to Laser OFF spectra Properties of the laser system: Efficiency ≈ 10% Selectivity ≈ 10 3 5s 2 1 S 0 5s 5p 1 P 1 5s 5d 1 D 2 510.6nm 643.8 nm 228.8nm Cd

9. 9 Mass scan at HRS (ISOLDE) in 2002; efficiency corrected in reality, „on a good day…“  M/M ≈ 1/4000 DM/M=7.5*10 -5 HRS design  ≥ 1/10 4 Request: Selectivity ! Isobar separation In Cs Cd Cd 2.000 In 17.000 with HRS !

10. 10 Request: Selectivity ! Chemistry in the transfer line between target and ion-source ↷ thermochromatography Deposition of Zn, Rb, Ag, In, Cd and Cs in a quartz tube with a temperature gradient  separation Cd, from Cs, In Prototype UC x target at CERN/ISOLDE with temperature-controlled quartz transfer-line  Oct. 2005 Diploma thesis C. Jost (2005)

11. 11 Surprises high [ g 7/2  g 9/2 ] 1 + state weakening of the g 7/2 -  g 9/2 residual interaction high Q  -value 130 In 81 OXBASH (B.A. Brown, Oct. 2003) 01-1- 473 3+3+ 1382 (old)1+1+ 1+1+ 895 0-0- 1441 1-1- 1906 1-1- 2515 2598 1-1- 0-0- 2181 (new) reduction of the TBME (1+) by 800 keV Full spectroscopy 130 Cd decay

12. 12 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Z N Sb Te I Xe Cs Ba 82 84 86 88 90 92 94 Snapshots: r-process paths for different neutron densities heaviest isotopes with measured T 1/2 g 9/2 d 5/2 s 1/2 g 7/2 d 3/2 h 11/2 g 9/2 p 1/2 p 3/2 f 5/2 f 7/2

13. 13 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Z N Sb Te I Xe Cs Ba 82 84 86 88 90 92 94 R-process path for n n =10 20 „waiting-point“ isotopes at n n =10 20 freeze-out n n =10 20

14. 14 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Z N Sb Te I Xe Cs Ba 82 84 86 88 90 92 94 „waiting-point“ isotopes at n n =10 23 freeze-out R-process paths for n n =10 20 and 10 23 (T 1/2 exp. : 28 Ni – 31 Ga, 36 Kr, 37 Rb, 47 Ag – 51 Sb) n n =10 23 n n =10 20

15. 15 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Z N Sb Te I Xe Cs Ba 82 84 86 88 90 92 94 (T 1/2 exp. : 28 Ni, 29 Cu, 47 Ag – 50 Sn) boulevard R-process boulevard for n n =10 20, 10 23 and 10 26 „waiting-point“ isotopes at n n =10 26 freeze-out n n =10 23 n n =10 26 n n =10 20

16. 16... resulting from new experimental and theoretical nuclear structure information: better understanding of shape of and matter flow through the major r-process bottle-neck at the A  130 N r,  peak no justification to question waiting-point concept (Langanke et al., PRL 83, 199; Nucl. Phys. News 10, 2000) no need to request sizeable effects from -induced reactions (Qian et al., PRC 55, 1997) Astrophysical consequences  r-process abundances in the Solar System and in UMP Halo stars......are governed by nuclear structure! Nuclear masses from AMDC, 2003 ETFSI-Q Normalized to N r,  ( 130 Te) Longer T 1/2 ! „short“ T 1/2 „long“ T 1/2

17. 17 Abundance clues and constraints Observations versus calculations - solar system - UMP halo stars Conditions for „main“ and „weak“ r-process - n-densities - entropies Split between the two r-processes - 129 I (Wasserburg et al.) - below N=82 R-process chronometric pairs - Th/Eu, Th/U - new: Th/Hf Ages of UMP stars, Galaxy and Universe Suggestions on r-process sites Galactic chemical evolution (Un-) importance of fission recycling

18. 18 Conclusion nuclear-physics data for explosive nucleosynthesis calculations still unsatisfactory !  better global models for all nuclear shapes (spherical, prolate, oblate, triaxial, tetrahedral,…) and all nuclear types (even-even, odd-particle, odd-odd)  more measurements masses ! gross  -decay properties level systematics full spectroscopy of selected key“ waiting-point isotopes Despite impressive experimental and theoretical progress, situation of with sufficiently large SP model space,