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- Institut für Kernchemie, Univ. Mainz, Germany - HGF VISTARS, Germany

Nuclear-Physics far from Stability and r-Process Nucleosynthesis. Karl-Ludwig Kratz. - Institut für Kernchemie, Univ. Mainz, Germany - HGF VISTARS, Germany - Department Of Physics, Univ. of Notre Dame, USA. r-process observables. Historically, nuclear astrophysics has always been

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- Institut für Kernchemie, Univ. Mainz, Germany - HGF VISTARS, Germany

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  1. Nuclear-Physics far from Stability and r-Process Nucleosynthesis Karl-Ludwig Kratz - Institut für Kernchemie, Univ. Mainz, Germany - HGF VISTARS, Germany - Department Of Physics, Univ. of Notre Dame, USA

  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 • nuclear masses Sn-values ↷ r-process path Qb, Sn-values ↷ theoretical b-decay properties, n-capture rates • b-decay properties T1/2 ↷ r-process progenitor abundances, Nr,prog Pn ↷ smoothing Nr,prog Nr,final (Nr,) • n-capture rates sRC + sDC ↷ smoothing Nr,prog during freeze-out • nuclear structure development extrapolation into unknown regions • fission modes SF, bdf, n- and n-induced fission ↷ “fission (re-) cycling”; r-chronometers

  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) T1/2 ofN=82“waiting-point” isotope130Cd82 (top of A130 Nr, peak) In 2006, altogether more than 50 r-process nucleihave been measured (at least) via their T1/2, 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. (see talk O. Arndt)

  5. 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

  6. 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

  7. 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)

  8. nn=1020 nn=1023 nn=1026 Z N r-Process paths 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)

  9. b-Decay properties T1/2, Pn gross b-strength properties from theoretical models, e.g. QRPA in comparison with experiments. Requests: (I) prediction / reproduction of correct experimental “number” (II) detailed nuclear-structure understanding ↷full spectroscopy of “key” isotopes, like 80Zn50 , 130Cd82. Total Error = 3.73 Total Error = 5.54 Pn-Values Half-lives QRPA (GT) QRPA (GT) QRPA (GT+ff) QRPA (GT+ff) (P. Möller et al., PR C67, 055802 (2003)) Total Error = 3.52 Total Error = 3.08

  10. T1/2x 3 T1/2: 3 Effects of T1/2 on r-process matter flow T1/2 (GT + ff) • Mass model: ETFSI-Q • all astro-parameters kept constant • r-process model: • “waiting-point approximation“ r-matter flow too slow r-matter flow too fast

  11. Nuclear masses Over the years, development of various types of mass models / formulas: • Weizsäcker formula • Local mass formulas • (e.g. Garvey-Kelson; NpNn) • Global approaches • (e.g. Duflo-Zuker; KUTY) • Macroscopic-microscopic models • (e.g. FRDM, ETFSI) • Microscopic models • (e.g. RMF; HFB) Comparison to NUBASE (2001) // (2003) FRDM (1992) srms = 0.669 // 0.616 [MeV] ETF-Q (1996) srms = 0.818 // 0.729 [MeV] HFB-2 (2002) srms = 0.674 [MeV] HFB-3 (2003) srms = 0.656 [MeV] HFB-4 (2003) srms = 0.680 [MeV] HFB-8 (2004) srms = 0.635 [MeV] HFB-9 (2005) srms = 0.733 [MeV] HFB-12 (2005) srms = ? No improvement of srms J. Rikovska Stone, J. Phys. G: Nucl. Part. Phys. 31 (2005) Main deficiencies at Nmagic ! D. Lunney et al., Rev. Mod. Phys. 75, No. 3 (2003)

  12. FRDM FRDM Exp Exp DZ HFB-9 HFB-8 Groote The N=82 shell gap as a function of Z (1) EFTSI-Q HFB-2 TheN=82shell closure dominates the matter flow of the „main“ r-process (nn≥1023). Definition „shell gap“: S2n(82) – S2n(84) ↷ paired neutrons. Therefore request: experimental masses and reliable model predictions for the respective N=82 waiting-point nuclei 125Tc to 131In A≈130 Nr, peak

  13. The N=82 shell gap as a function of Z (2) Definition „shell gap“: S2n(81) – S2n(83) ↷ unpaired neutrons. Large odd-even Z staggering for „microscopic“ HFB models ‼ HFB-9 FRDM FRDM EFTSI-Q DZ Groote Exp Exp HFB-8 HFB-2

  14. Effects of nuclear masses on Nr, fits T1/2+Pnand allastro-parameterskeptconstant!

  15. From classical to high-entropy wind model SO FAR, site-independent parameter study within classicalWaiting-Point Model understand effects of nuclear-physics input on Nr,calc NOW, more realistic r-process model High-Entropy Wind of SN II “best” nuclear-physics input full dynamical network start with a-process charged-particle freeze-out  n-rich seed beyond N=50 (94Kr, 100Sr,…) for subsequentr-process avoids N=50 “bottle neck” in classical model ! Three main parameters: electron abundanceYe= Yp = 1 – Yn radiation entropy S ~ T³·r expansion speed vexp process durations taand tr

  16. Synthesizing selected mass region S=196 + 261 + 280 Superposition of individual S-components Pb Th U

  17. Superposition of 5 S-sequences to reproduce the Nr, pattern (100<A<240) N=50 N=82 N=126 Th, U r-process chronometers „weak“ r-process (Thesis K. Farouqi, 2005 ) Basis for detailed astrophysical parameter studies

  18. Calculated r-process abundances as function of neutron densities (K.-L. Kratz, B. Pfeiffer, 2005)

  19. Abundance predictions as function of nn “main” “main” “weak” “weak” r-process computations for selected elements r-process computations for selected isotopes

  20. r-Process elemental abundances “weak” r-process (see talk F. Montes) “main” r-process Solar system Simmerer et al., 2004 CS 22892-052 Sneden et al., 2003

  21. Conclusion Nuclear-physics data for r-process calculations still unsatisfactory ! • better global models for all nuclear shapes (spherical, prolate, oblate, triaxial, tetrahedral,…) and all nuclear types (even-even, even-odd, odd-even , odd-odd) • more measurements masses ! gross b-decay properties fission properties full spectroscopy of selected “key“ waiting-point isotopes

  22. 78Cu49 29 Example “future“ GSI experiment Full understanding of shell structure of “key isotope“78Ni • Mass measurement ↷ Qb, SnT1/2 + Pn, sng • g-spectroscopy ↷ Eℓ and log(ft) of np1/2pp3/2T1/2 • Eℓ and log(ft) of ng9/2pg9/2Pn • pn interaction 0+ 159 ms 0+ 120 ms Folded - Yukawa Woods - Saxon 78Ni50 78Ni50 Q = 10.45 ± 1.17 MeV (Audi ´03) Lipkin - Nogami 28 28 Lipkin - Nogami ≈ 1+nf5/2 pf7/2 9.6% 3.5 6.93 1+nf5/2 pf5/2 12.8% 3.6 6.34 ≈ 1+ng9/2 pg9/2 45.7% 3.5 5.46 1+ng9/2 pg9/2 51.1% 3.6 4.97 1+ng9/2 pg9/2 Sn= 4.24±0.57 MeV 1+nf5/2 pf7/2 6.6% 4.8 3.6% 4.9 4.35 4.23 1+nf5/2 pf7/2 5.4% 5.0 3.95 1+nf5/2 pf7/2 0.5% 6.0 3.65 1+nf5/2 pf7/2 3.4% 5.3 3.00 1+np1/2 pp3/2 32.3% 4.6 2.76 1+np1/2 pp3/2 27.9% 4.6 ≈ 2.48 ≈ ng9/2 pp3/2 ng9/2 pp3/2 0 0 78Cu49 29

  23. … as an example for long “diffusion time” • from KCh Mainz → GSI Darmstadt • from experimentalist → theoretician

  24. Among the … Eleven Greatest Unanswered Questions of Physics (Discover Magazine, 2002) “After the discovery of “antimatter” and “dark matter”, we have recently found the existence of “doesn’t matter”, which seems to have no effect on the Universe whatsoever.” … How were the heavy elements from Fe to U made?

  25. Nuclear physics in the r-process • Fission rates and distributions: • n-induced • spontaneous • b-delayed b-delayed n-emissionbranchings(final abundances) b-decay half-lives(progenitor abundances, process speed) • Neutron-capture rates • for A>130 in slow freeze-out • for A<130 maybe in a “weak” r-process ? n-physics ? Seed productionrates (aaa,aan, a2n, ..) Masses (Sn)(location of the path)

  26. N/Z g 9/2 126 g 9/2 p 1/2 i f 13/2 112 5/2 p h ;f 3/2 i 9/2 5/2 13/2 p h 1/2 9/2 f p 7/2 3/2 f 7/2 h 11/2 70 h 11/2 g d 7/2 3/2 g d 7/2 s 3/2 1/2 s d 1/2 5/2 50 d 5/2 g g 9/2 9/2 40 p 1/2 f 5/2 f p 5/2 1/2 132Sn 82 50 82 Motivation: Nuclear structure R -abundances ) 0 w h of 7.0 Units ( 6.5 Energies 6.0 5.5 Single – Neutron 5.0 FK²L (Ap.J. 403 ; 1993) “..the calculated r-abundance ‘hole‘ in the A  120 region reflects ... the weakening of the shell strength ... below “ 70% 10% 100% 40% Strength of ℓ -Term 2 B. Pfeiffer et al., Acta Phys. Polon. B27 (1996)

  27. Nuclear-Physics Input from “internally consistent“ models, with local improvements. Waiting-point approximation requires Sn defines r-process path (Saha equ.) T½ determines progenitor abundances (Nr,prog) Pxn  smoothens Nr,prog  Nr, Start with input for Nuclear-Mass Model FRDM, ETFSI-Q, HFB-2,... macroscopic microscopic finite-range folded Yukawa droplet single particle Q, Sn, 2, s.p. wave fcts. Shell Model QRPA(global), OXBASH, ANTOINE,... Gamow-Teller strength functions T½, Pxn, EQP, JQP, QP  In addition • experimental data (up to Dec. 2003) • short-range model extrapolation • due to known nuclear-structure developments • inclusion of ff-strength (Gr.Th.)

  28. 132Sn 50 (n,) 134 135 136 137 133 131 165ms Pn~85% 278ms (n,) 134 135 132 130 162ms 131 132 133 129 46ms(g) 158ms(m) 130 128 133In84 49 131In82 49 130Cd82 48 127 129Ag82 47 r-process path 126 (n,) 128Pd82 46 127Rh82 45 R-abundance peaks and neutron-shell numbers ...still today important r-process properties to be studied experimentally and theoretically. already B²FH (Revs. Mod. Phys. 29; 1957) C.D. Coryell (J. Chem. Educ. 38; 1961) b “climb up the staircase“ at N=82; major waiting point nuclei; “break-through pair“131In, 133In; K.-L. Kratz (Revs. Mod. Astr. 1; 1988) climb up the N= 82 ladder ... A  130 “bottle neck“ total r-process duration r “association with the rising side of major peaks in the abundance curve“

  29. 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 and dn counting 1+ 4.1 2.0 Problems: high background from -surface ionized 130In, 130Cs -molecular ions [40Ca90Br]+ T1/2(GT) = 0.3 s 1.0 1- 0 Request:SELECTIVITY !

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

  31. Request: Selectivity ! 130Cd 1669 keV 130Sb 1749 keV 130Cd 1732 keV Laser ON Laser OFF Energy [keV] Laser ion-source (RILIS) Laser ON Comparison of Laser ON to Laser OFF spectra Laser OFF g-singles spectrum Chemically selective, three-step laser ionization of Ag into continuum Properties of the laser system: Efficiency ≈ 10% Selectivity ≈ 103

  32. The N=82 shell gap as a function of Z TheN=82shell closure dominates the matter flow of the „main“ r-process (nn≥1023). S2n(81) – S2n(83) ↷ unpaired neutrons. S2n(82) – S2n(84) ↷ paired neutrons Therefore request: experimental masses and more reliable model predictions A≈130 Nr, peak FRDM FRDM HFB 9 HFB 9 Groote EFTSI-Q Groote EFTSI-Q

  33. The -process 3<T9<6 • NSE: All nuclear reactions via strong and electro-magnetic interactions are very fast when compared with dynamical time scales. At T9~6, -particles become the dominant constituent of the hot bubble! Recombination of the -particles is possible via: • 3→ 12C and • ++n → 9Be, followed by 9Be(,n) 12C • Charged-particle freeze-out at T9~ 3 with: • Dominant part of -particles ~ 80% • Some heavy nuclei beyond iron (80 <A< 110) • Probably a little bit of free neutrons  Seed composition for a subsequent r-process.

  34. For a given blob of matter behind the shock front above the proto-neutron star : define three parameters: • Electron abundance: Ye=Yp=1-Yn Example: Ye=0.45  55% neutrons & 45% protons • Radiation entropy: Srad~ T3/r • Expansion speed Vexp determines process durations  and r : Example: Vexp= 7500 km/s, R0= 130 km   = 35 ms, r= 280 ms

  35. Seed nuclei after an -rich freeze-out S=200, Vexp=7500 km/s • Neutron-rich seed beyond N=50 • difference to „classical“ r-process with 56Fe seed • avoids N=50 r-process bottle-neck •  seed nuclei: 94Kr, 100Sr (87Se, 103Y, 89Br, 84Ge, 95Kr, 76Ni, 95Rb below 5%)

  36. Definition of the r-process freeze-out Classical r-process:nn, T9= const up to break-out of (nγγn) equilibrium! This means: (n,γ) < (γ,n) instantaneous freeze-out! No need of neutron capture rates! Dynamical r-process: nn = f(t,T9), T9= f(t) This means: (nn) <  (n,γ) and (nn) < (γ,n) no instantaneous freeze-out! Neutron capture rates are needed!

  37. Effect of neutron-capture rates on the A=130 peak Freeze-out is fast  no significant effect on A=130 peak

  38. Effect of neutron-capture rates on the A=195 peak Freeze-out is slow  significant effect on A=195 peak

  39. Synthesizing the A=130 peak S=196 Process duration: 146 ms

  40. Synthesizing the A=195 peak S=261 Process duration: 327 ms not yet enough Pb Th U

  41. Present status r-process-rich Galactic halo stars (C. Sneden, J.J. Cowan, et al.)

  42. Reproduce isotopic Nr, distribution(lsq-fits; A > 80, 120) CS 22892-052 abundances scaled solar r-process scaled theoretical solar r-process Zr Pt Os Pb Cd Ru Ba 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

  43. Cosmo chronology with Thorium   U  

  44. GSI-Experiment E040 (2000) •238U beam @ 750MeV/u on Pb-Target Projectile fission produces neutron-rich nuclei • Separation and identification of fission products with the FRS • Measuring T1/2 and Pn after implantation of nuclei in Si-stack T1/2 = 296 (35)ms T1/2 = 334 (14)ms J. Pereira, NSCL and R. Kessler, Uni Mainz

  45. Example: recent experiment 0+ 0+ 110Zr 110Zr … Q  9.27 MeV Q  9.27 MeV 1+ 7.64 1+ 7.04 6.44 1+ GT GT 1+ 5.22 Sn  3.73 MeV 1+ Levels [g9/2g7/2] Sn  3.21 MeV 73% 10% 1.13 1+ 2- 0 B. Pfeiffer et al., Acta Phys. Polon. B27 (1996) 3- 0 110Nb Zr ... a new double-magic „waiting-point“ nucleus? 110 40 70 Beta-decay Normal shell strength strongly deformed (2=0.31) Shell strength quenched spherical T½ = 14 ms Pn = 0.7 % T½ = 88 ms Pn = 8 % 99% 1.67 0.85 110Nb Exp. 5028 at NSCL/MSU; Nov. 2005; to be continued at GSI ?

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