Nuclear structure and the A 130 r-process abundance peak Karl-Ludwig Kratz - Institut fuer Kernchemie, Univ. Mainz, Germany - HGF VISTARS, Germany - Department of Physics, Univ. of Notre Dame, USA
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, N r, T 9 =1.35; n n =10 20-10 28 Pb, Bi α-, β-decays fission Ga Ge Sr Zr Ru Cd Mo Pd Sn Y Rh Nb Ag CS 22892-052 abundances scaled solar r-process scaled theoretical solar r-process Pt Ba Os Nd Dy Gd Ce Sm Er Yb Ir Hf La Pr Eu Ho Tb Lu Tm Elemental abundances in UMP halo stars Au Pb Th U δ [ ] 16 14 12 10 8 6 4 2 0 r-process observables ALLENDE INCLUSION EK-1-4-1 38 40 42 44 46 48-2 Mass number Mass number isotopic composition Ca, Ti, Cr, Zr, Mo, Ru, Nd, Sm, Dy r-enhanced FUN-anomalies in meteoritic samples
Solar system s- and r-process abundance peaks Solar system s- and r-process abundance peaks SS isotopic deconvolution by s- and r-process Log ε(a) = log 10 (N A /N H ) + 12
CS 22892-052 elemetal abundances Cowan et al. (2005) 57 elements observed. More than any star except the Sun. Log ε(a) = Log 10 (N A /N H ) + 12
Nuclear-data needs for the classical r-process nuclear masses S n -values r-process path Q β, S n -values theoretical β-decay properties, n-capture rates β-decay properties T 1/2 r-process progenitor abundances, N r,prog β-decay freeze-out P n smoothing N r,prog N r,final (N r, ) neutron capture rates fission modes σ RC + σ DC smoothing N r,prog during freeze-out SF, βdf, n- and ν-induced fission fission (re-) cycling ; r-chronometers nuclear structure development - level systematics - short-range extrapolation into unknown regions
E(2+) - landscape 90 A 150 Z E(2+) reduced pairing rigid rotors g9/2 interaction g7/2 shell quenching 90Zr 132Sn 96Zr 50 d5/2 56 110Zr 60 s1/2 r-pro g7/2 h11/2 magic shells/subshells shape transitions/coexistence intruder states identical bands cess path d3/2 50 82 g9/2 40 N
The A 130 N r, peak already B²FH (Revs. Mod. Phys. 29; 1957) C.D. Coryell (J. Chem. Educ. 38; 1961)...still today important r-process properties to be studied experimentally and theoretically. 131 132 Sn 50 133 P n ~85% (n,γ) 165ms 134 135 136 137 130 278ms 162ms 131 In 82 49 (n,γ) 132 133 In 84 49 134 135 129 158ms(m) 46ms(g) 130 Cd 82 48 131 132 133 128 129 Ag 82 47 130 127 128 Pd 82 46 β climb up the staircase at N=82; major waiting point nuclei; break-through pair 131 In, 133 In; association with the rising side of major peaks in the abundance curve r-process path 126 (n,γ) 127 Rh 82 45 K.-L. Kratz (Revs. Mod. Astr. 1; 1988) climb up the N= 82 ladder... A 130 bottle neck total r-process duration τ r
Shape of N r, abundance peak rising wing 122<A<130 solar r abundances short T 1/2 neutrino induced reactions? Qian,Haxton et al. (1997) waiting-point concept breaks down? Martinez-P. & Langanke (1999) nuclear structure below 132 Sn not understood? Kratz et al. (since 1993) importance of νg 7/2 πg 9/2 GT position of νg 7/2 SP state νd 3/2 rel. to νh 11/2 spin-orbit splitting ν3p 3/2 - ν3p 1/2 ν2f 7/2 - ν2f 5/2 π2p 3/2 - π2p 1/2 π1f 7/2 - π1f 5/2 N=82 shell quenching QRPA (Nilsson, Woods-Saxon,Folded Yukawa) OXBASH
The r-process waiting-point nucleus 130 Cd...obtain a physically consistent picture! T 1/2, Q β, E(1 + ), I β (1 + ), log ft S n Q β 7.0 8.9 J π =1 + {νg 7/2, πg 9/2 } 2QP 4QP 1.2 2.9 free choice of combinations: low E(1 + ) with low Q β high E(1 + ) with low Q β low E(1 + ) with high Q β high E(1 + ) with high Q β T 1/2 (GT) 233 ms 1130 ms 76 ms 246 ms
E*[MeV] What is known experimentally? 131 β 49 In 131 82 50 Sn 81 3 2,5 I J π E β Level log(ft) νg 7/2 7/2 + 2434 90% 4.4 I β J π E Level log(ft) 2565 89% 4.0 2 1,5 5/2 + 1655 P n = 4.4% T 1/2 = 157 ms 1 P n = 2.2% T 1/2 = 280 ms (Fogelberg, 2004) 0,5 0 1/2 + 11/2-3/2 + Experiment 332 65 < 20% > 5.6 νs 1/2 νd 3/2 νh 11/2 QRPA (FY/LN) 524 282 0 0 2.3% 6.3
Level systematics of the lowest 1 + state in neutron-rich even-mass In isotopes Experimental OXBASH (B.A. Brown, Oct. 2003) 1 + 2120 1 + 2181 (new) 1 + 688 1 + 243 3 + 0 3 + 0 3 + 0 3 + 389 3 + 473 124 In 75 126 In 77 1 + 1173 128 In 79 1731 kev 1 + 1382 (old) 1-0 1-0 Reduction of the TBME (1+) by 800 kev 130 In 81 130 In 81 Configuration 3 + : νd 3/2 πg 9/2 Configuration 1 + : νg 7/2 πg 9/2 Configuration 1 - : νh 11/2 πg 9/2
3 2,5 Beta-decay odd-mass, N=82 isotones νsp states in N=81 isotones S 1n =5.246MeV S 1n =3.98MeV S 1n =3.59MeV E*[MeV] νg 7/2 2565 2607 89% 4.0 7/2 + 7/2 + 67% 7/2 + 88% 4.0 S 1n =2.84MeV 2648 264345% νg 7/2 2637 4.1 4.25 24% 4.5 2 1,5 P n =4.4% P n =9.3% P 1n =29% P 2n = 2% P 1n =39% P 2n =11% P 3n = 4.5% P 1n =25% P 2n =45% P 3n =11% S 1n =1.81MeV P 4n = 8.5% P 5n = 1% 1 0,5 νs 1/2 νd 3/2 524 282 601 1/2 + 1/2 + 3/2 + 414 3/2+ 3/2 + 331 728 1/2 + 1/2 + 814 472 3/2 + 908 536 0 νh 11/2 131 Sn 81 50 0 2.3% 6.3 11/2-1.2% 11/2-11/2-0.6% 11/2-6.3 0.9% 6.4 129 Cd 81 127 Pd 81 125 Ru 81 123 Mo 81 48 46 44 42 6.4 0.5% 6.45 I β log(ft)
E*[MeV] 3,5 S n = 5.02 MeV Beta-decay even-mass, N=82 isotones 2QP states in N=81 isotones S n = 4.05 MeV S n = 4.05 MeV 3 J π log(ft) 1 + νg 7/2 πg 9/2 3.5 2,5 2 1,5 νg 7/2 πg 9/2 1 + 1 + 4.25 P n 10% P n 15% 3.9 1 + 3.7 P 1n 18% P 2n 2% 1 + 3.6 S n = 2.30MeV P 1n 77% P 2n 16% P 3n 3% P 1n 70% P 2n 4% P 3n 17% P 4n 4% S n = 1.49MeV 1 3 + µs isomer! 0,5 νd 3/2 πg 9/2 νd 3/2 πg 9/2 3 + 3+ 3 + 3 + 3+ 0 1 - νh 11/2 πg 9/2 130 In 81 1-1 - 1-1 - νh 11/2 πg 9/2 128 49 Ag 126 81 Rh 124 81 Tc 122 47 81 Nb 45 43 41 81
Effects of N=82 shell quenching Single Neutron Energies (Units of hω 0 ) 7.0 6.5 6.0 5.5 5.0 g 9/2 p 1/2 f 5/2 p 3/2 h 9/2 f 7/2 i 13/2 g 9/2 i 13/2 p 1/2 p 3/2 f 7/2 h h 70 11/2 11/2 d 3/2 g 7/2 g 7/2 d 3/2 s 1/2 126 82 N/Z 112 h 9/2 ;f 5/2 s 1/2 d 5/2 50 d 5/2 g g 9/2 9/2 40 p 1/2 f 5/2 f 5/2 p 1/2 high-j orbitals (e.g. νh 11/2 ) low-j orbitals (e.g. νd 3/2 ) evtl. crossing of orbitals new magic numbers / shell gaps (e.g. 110 Zr 70, 170 Ce 112 ) 40 58 change of T 1/2? 100% 70% 40% 10% Strength of l 2 -Term B. Pfeiffer et al., Acta Phys. Polon. B27 (1996)
Beta-decay of 129 Ag isomers Separation of isomers by fine-tuning of laser frequency πg 9/2 πp 1/2 127 Ag πp 1/2 πg 9/2 30% 70% 158ms 46ms πg 9/2 πp 1/2 129m Ag 82 129g Ag 82 T 1/2 (g)=(46 +5-9 ) ms T 1/2 (m)=(158±60) ms
129 Cd 81 βdn - emission 129g Cd 129m Cd νh 11/2 Q β GT (9/2,11/2,13/2) - γ high l n 1 + 2 - S n γ 128 In 1 - (3 + ) νd 3/2 νh 11/2 GT (Q β +x) (1/2,3/2,5/2) + γ low l n 1 + 2 - S n γ 128 In 1 - (3 + ) 129 In 129 In hard βdn-spectrum mainly outer 3 He ring soft βdn-spectrum mainly inner 3 He ring of neutron longcounter 2 T 1/2 components T ½ ( 129g Cd) = 242(8) ms T ½ ( 129m Cd) = 104(6) ms O. Arndt (Diploma Thesis; 2003)
RIB experiments: (d,p) in inverse kinematics E L, l n (J π ),C²S n-capture rate <σ> RC = 0.12 mb SMOKER TEDKA
Spin-orbit splitting, N=83
Astrophysical consequences (I) Dynamic r-process calculations (T 1/2, P n from exp. + QRPA S n, Q β from AMDC + ETFSI-Q) 128 Pd Classical waiting point concept T 1/2 (N=82)~N r, too simple! 132 Sn 131 In apart from T 1/2 (N=82) also effect from S n (N=83) on N r,prog N r, N= 82 waiting-points 130 Cd 129 Ag N(mag.) r-progenitors act as waiting points for different n n - ranges
Astrophysical consequences (II)...mainly resulting from new nuclear structure information: better understanding of formation and shape of, as well as r-process matter flow through 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 ν-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! short T 1/2 long T1/2 Nuclear masses from AMDC, 2003 ETFSI-Q Normalized to N r, (130 Te)
nuclear-physics data Conclusion Despite impressive experimental and theoretical progress, situation of for r-process 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) with large model space more measurements masses! gross β-decay properties level systematics full spectroscopy of selected key waiting-point isotopes