1 / 18

Decay Studies and Observables of r-Process Nuclei

Explore the history, progress, and measurements of r-process isotopes, focusing on the decay studies and r-process observables, investigating nuclear astrophysics interpretations and processes.

latimore
Download Presentation

Decay Studies and Observables of r-Process Nuclei

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Decay studies of r-process nuclei sng T1/2 Sn Pn  Karl-Ludwig Kratz • Max-Planck-Institut für Chemie, Mainz, Germany • Department of Physics, Univ. of Notre Dame, USA HRIBF 2006

  2. R-process observables • 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). Solar system isotopic abundances, Nr, T9=1.35; nn=1020 - 1028 , Bi r-process observables CS 22892-052 abundances isotopic composition Ca, Ti, Cr, Zr, Mo, Ru, Nd, Sm, Dy ↷ r-enhanced scaled solar r-process ALLENDE INCLUSION EK-1-4-1 scaled theoretical solar r-process Zr Pt Os Pb Cd Ru Ba d [‰] Nd Sn Sr Ga Pd Dy Mo Gd Er Ge Sm Ce Yb Ir Hf Y Rh La Nb Ag Ho Eu Pr Tb Au Lu Th Tm U Mass number Elemental abundances in UMP halo stars “FUN-anomalies” in meteoritic samples

  3. b-decay freeze-out Nuclear-data needs for the classical r-process • b-decay properties T1/2r-process progenitor abundances, Nr,prog Pn  smoothing Nr,prog Nr,final (Nr,) • nuclear masses Sn-values  r-process path Qb, Sn-values  theoretical b-decay properties, n-capture rates • neutron capture rates sRC + sDC  smoothing Nr,prog during freeze-out • fission modes SF, bdf, n- and n-induced fission  “fission (re-) cycling”; r-chronometers • nuclear structure development • level systematics • “understanding” b-decay properties • - short-range extrapolation into unknown regions

  4. History and progress in measuring r-process nuclei Definition: r-process isotopes lyingin the process path at freeze-out ↷ when r-process falls out of (n,g)-(g,n) equilibrium even-neutron isotopes↷“waiting points” important nuclear-physics property T1/2 odd-neutron isotopes ↷connecting the waiting points important nuclear-physics property Snsn.g In 1986 a new r-process astrophysics era started: at the ISOL facilities OSIRIS,TRISTAN and SC-ISOLDE T1/2 ofN=50“waiting-point” isotope80Zn50 (top of A80 Nr, peak; “weak” r-process) T1/2 ofN=82“waiting-point” isotope130Cd82 (top of A130 Nr, peak; “main” r-process) In 2006, altogether more than 50 r-process nucleihave been measured, which lie in the process path at freeze-out. • These r-process isotopes range from 68Fe to 139Sb. The large majority of these exotic nuclei was identified at CERN/ISOLDE via the decay mode of b–delayed neutron emission.

  5. What we knew already in 1986 ... Shell-model (QRPA; Nilsson/BCS) prediction 1+ 1.0 Q = 8.0 MeV T1/2 = 230 ms 1+ IKMz – 155R(1986) 6.0 1+ T1/2 = (195 ± 35) ms 1+ 5.0 1+ 1+ 4.0 1+ K.-L. Kratz et al (Z. Physik A325; 1986) 3.0 g7/2, g9/2 Exp. at old SC-ISOLDE with plasma ion-source quartz transfer line and dn counting 1+ 4.1 2.0 T1/2(GT) = 0.3 s Problems: high background from -surface ionized 130In, 130Cs -molecular ions [40Ca90Br]+ 1.0 1- 0 Request:SELECTIVITY !

  6. The r-process “waiting-point“ nucleus 130Cd ...obtain a physically consistent picture! T1/2, Q, E(1+), I(1+), log ft Q Sn 7.0 8.9 J=1+ {g7/2, g9/2} 2QP 4QP 1.2 2.9 “free choice” of combinations: T1/2(GT) 233 ms 1130 ms 76 ms 246 ms low E(1+) with low Qb high E(1+) with low Qb low E(1+) with high Qb high E(1+) with high Qb (log ft=4.1)

  7. Request: Selectivity ! Sb Te I Xe Sn Cd In Ag Cs Why ? the Ag “needle” in the Cs “haystack” How? Improvements since 1993 at PS-Booster ISOLDE • Fast UCx target • Neutron converter • Laser ion-source • Hyperfine splitting • Isobar separation • Repeller • Chemical separation • Multi-coincidence setup 50 800 >105

  8. Request: Selectivity ! 130Cd 1669 keV 130Sb 1749 keV 130Cd 1732 keV Laser ON Laser OFF Energy [keV] Laser ion-source (RILIS) Laser ON 510.6nm Comparison of Laser ON to Laser OFF spectra 5s 5d1D2 643.8nm 5s 5p1P1 Laser OFF 228.8nm 5s2 1S0 Cd g-singles spectrum Chemically selective, three-step laser ionisation of Cd into continuum Properties of the laser system: Efficiency ≈ 10% Selectivity ≈ 103

  9. Request: Selectivity ! Isobar separation HRS design DM/M ≥ 1/104 in reality, „on a good day…“ DM/M ≈ 1/4000 In Cd 2.000 ! DM/M=7.5*10-5 In 17.000 Cs Cd with HRS Mass scan at HRS (ISOLDE) in 2002; efficiency corrected

  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 UCx target at CERN/ISOLDE with temperature-controlled quartz transfer-line Oct. 2005 Diploma thesis C. Jost (2005)

  11. Full spectroscopy 130Cd decay • Surprises • high [ng7/2pg9/2] 1+ state • weakening of the ng7/2 - pg9/2 • residual interaction • high Qb-value OXBASH (B.A. Brown, Oct. 2003) 2598 1- 2515 0- 1+ 2181 (new) reduction of the TBME (1+) by 800 keV 1906 1- 1441 1- 1+ 1382 (old) 0- 895 473 3+ 1- 0 130In81

  12. Z N Snapshots: r-process paths for different neutron densities 82 84 86 88 90 92 94 Ba Cs Xe heaviest isotopes with measured T1/2 I Te Sb Sn In Cd Ag g9/2 Pd Rh Ru Tc Mo Nb Zr p1/2 Y Sr Rb p3/2 Kr Br Se As f5/2 Ge Ga Zn Cu Ni f7/2 Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 h11/2 d3/2 g9/2 d5/2 g7/2 s1/2

  13. nn=1020 Z N R-process path for nn=1020 82 84 86 88 90 92 94 Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se As Ge Ga Zn Cu Ni Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 „waiting-point“ isotopes at nn=1020 freeze-out

  14. nn=1020 nn=1023 Z N R-process paths for nn=1020 and 1023 82 84 86 88 90 92 94 Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se As Ge Ga Zn Cu Ni Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 „waiting-point“ isotopes at nn=1023 freeze-out (T1/2 exp. : 28Ni – 31Ga, 36Kr, 37Rb,47Ag – 51Sb)

  15. nn=1020 nn=1023 nn=1026 Z N R-process boulevard for nn=1020, 1023 and 1026 82 84 86 88 90 92 94 Ba Cs Xe I Te Sb Sn In Cd Ag Pd Rh Ru Tc Mo Nb Zr Y Sr Rb Kr Br Se As Ge Ga Zn Cu Ni Co Fe 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 8082 „waiting-point“ isotopes at nn=1026 freeze-out (T1/2 exp. : 28Ni, 29Cu, 47Ag – 50Sn)

  16. Astrophysical consequences Longer T1/2! • ... 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 Nr, 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 n-induced reactions • (Qian et al., PRC 55, 1997)  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 Nr,(130Te) „short“ T1/2 „long“ T1/2

  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 - 129I (Wasserburg et al.) • - below N=82 • (Un-) importance of fission recycling • Suggestions on r-process sites • Galactic chemical evolution • R-process chronometric pairs - Th/Eu, Th/U • - new: Th/Hf • Ages of UMP stars, Galaxy and Universe

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

More Related