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Transcript of Hirschegg XXXIV ‘06 - Institut für Kernchemie, Univ. Mainz, Germany - HGF VISTARS, Germany -...
Hirschegg XXXIV ‘06
- Institut für Kernchemie, Univ. Mainz, Germany- HGF VISTARS, Germany- Department Of Physics, Univ. of Notre Dame, USA
Karl-Ludwig Kratz
Nuclear-Physics far from Stabilityand
r-Process Nucleosynthesis
Hirschegg XXXIV ‘06
-2
0
2
4
6
8
10
12
14
16
38 40 42 44 46 48
Mass number
scaled theoretical solar r-processscaled solar r-process
Nb
Zr
Y
SrMo
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
ThU
GaGe
CdSn
Elemental abundances in UMP halo stars
r-process observables
Solar system isotopic abundances, Nr,
“FUN-anomalies” in meteoritic samples
isotopiccomposition 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 INCLUSIONEK-1-4-1
Mass number
CS 22892-052 abundances
T9=1.35; nn=1020 - 1028
r-process observables
, Bi
Hirschegg XXXIV ‘06
Nuclear-data needs for the classical r-process
nuclear masses
Sn-values r-process ↷ pathQ, Sn-values theoretical ↷ -decay properties, n-capture rates
-decay properties
n-capture rates
fission modes
nuclear structure development
T1/2 r-process ↷ progenitor abundances, Nr,prog
Pn smoothing N↷ r,prog Nr,final (Nr,)
RC +DC smoothing N↷ r,prog during freeze-out
SF, df, n- and -induced fission
↷ “fission (re-) cycling”; r-chronometers
extrapolation into unknown regions
-decayfreeze-out
Hirschegg XXXIV ‘06
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 T1/2
odd-neutron isotopes ↷ connecting the waiting points important nuclear-physics property Sn n.
In 1986 a new r-process astrophysics era started: at the ISOL facilities OSIRIS, TRISTAN and SC-ISOLDE T1/2 of N=50 “waiting-point” isotope 80Zn50 (top of A80 Nr, peak)
T1/2 of N=82 “waiting-point” isotope 130Cd82 (top of A130 Nr, peak)
In 2006, altogether more than 50 r-process nuclei have 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/ISOLDEvia the decay mode of
–delayed neutron emission. (see talk O. Arndt)
Hirschegg XXXIV ‘06
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82Fe
CoNi
CuZn
GaGe
AsSe
BrKr
Rb
SrY
ZrNb
MoTc
RuRh
PdAg
CdIn
Sn
Z N
SbTe
IXe
CsBa
82 84 86 88 90 92 94
Snapshots: r-process paths for different neutron densities
heaviest isotopes with measured T1/2
g9/2 d5/2 s1/2 g7/2 d3/2 h11/2
g9/2
p1/2
p3/2
f5/2
f7/2
Hirschegg XXXIV ‘06
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82Fe
CoNi
CuZn
GaGe
AsSe
BrKr
Rb
SrY
ZrNb
MoTc
RuRh
PdAg
CdIn
Sn
Z N
SbTe
IXe
CsBa
82 84 86 88 90 92 94
r-Process path for nn=1020
„waiting-point“ isotopes at nn=1020 freeze-out
nn=1020
Hirschegg XXXIV ‘06
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82Fe
CoNi
CuZn
GaGe
AsSe
BrKr
Rb
SrY
ZrNb
MoTc
RuRh
PdAg
CdIn
Sn
Z N
SbTe
IXe
CsBa
82 84 86 88 90 92 94
„waiting-point“ isotopes at nn=1023 freeze-out
r-Process paths for nn=1020 and 1023
(T1/2 exp. : 28Ni – 31Ga, 36Kr, 37Rb,47Ag – 51Sb)
nn=1023
nn=1020
Hirschegg XXXIV ‘06
42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82Fe
CoNi
CuZn
GaGe
AsSe
BrKr
Rb
SrY
ZrNb
MoTc
RuRh
PdAg
CdIn
Sn
Z N
SbTe
IXe
CsBa
82 84 86 88 90 92 94
(T1/2 exp. : 28Ni, 29Cu, 47Ag – 50Sn)
r-Process paths for nn=1020, 1023 and 1026
nn=1023
nn=1026
nn=1020
„waiting-point“ isotopes at nn=1026 freeze-out
Hirschegg XXXIV ‘06
Total Error = 5.54
Total Error = 3.52
Total Error = 3.73
Total Error = 3.08
Pn-ValuesHalf-lives
(P. Möller et al.,PR C67, 055802 (2003))
-Decay properties
T1/2, Pn gross -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.
QRPA (GT)
QRPA (GT+ff)
QRPA (GT)
QRPA (GT+ff)
Hirschegg XXXIV ‘06
T1/2 : 3
r-matter flow too slow r-matter flow too fast
Effects of T1/2 on r-process matter flow
Mass model: ETFSI-Q- all astro-parameters kept constant
r-process model: “waiting-point approximation“
T1/2 x 3
T1/2 (GT + ff)
Hirschegg XXXIV ‘06D. Lunney et al., Rev. Mod. Phys. 75, No. 3 (2003)
Nuclear masses
• Weizsäcker formula• Local mass formulas (e.g. Garvey-Kelson; NN)• 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)rms = 0.669 // 0.616 [MeV]ETF-Q (1996) rms = 0.818 // 0.729 [MeV]HFB-2 (2002) rms = 0.674 [MeV]HFB-3 (2003) rms = 0.656 [MeV]HFB-4 (2003) rms = 0.680 [MeV]
HFB-8 (2004) rms = 0.635 [MeV]HFB-9 (2005) rms = 0.733 [MeV]
HFB-12 (2005) rms = ?
Over the years, development of various types of mass models / formulas:
No improvement of rms
J. Rikovska Stone, J. Phys. G: Nucl. Part. Phys. 31 (2005)
Main deficiencies at Nmagic !
Hirschegg XXXIV ‘06
The N=82 shell gap as a function of Z (1)
FRDM FRDM
DZ
Groote
EFTSI-QHFB-2
HFB-8
HFB-9
Exp Exp
A≈130 Nr, peak
The N=82 shell 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
Hirschegg XXXIV ‘06
FRDM
EFTSI-Q
Groote
HFB-8
HFB-2
HFB-9
FRDM
DZ
The N=82 shell gap as a function of Z (2)
Exp Exp
Definition „shell gap“: S2n(81) – S2n(83) ↷ unpaired neutrons.
Large odd-even Z staggering for „microscopic“ HFB models ‼
Hirschegg XXXIV ‘06
Effects of nuclear masses on Nr, fits
T1/2+Pn and all astro-parameters kept constant !
Hirschegg XXXIV ‘06
SO FAR, site-independent parameter studywithin classical Waiting-Point Model
understand effects of nuclear-physics input on Nr,calc
NOW, more realistic r-process model
“best” nuclear-physics inputfull dynamical network
High-Entropy Wind of SN II
start with -processcharged-particle freeze-out
n-rich seed beyond N=50 (94Kr, 100Sr,…)for subsequent r-process avoids N=50 “bottle neck” in classical model !
Three main parameters:
electron abundance Ye = Yp = 1 – Yn
radiation entropy S ~ T³·expansion speed vexp process durations and r
From classical to high-entropy wind model
Hirschegg XXXIV ‘06
Synthesizing selected mass region
S=196 + 261 + 280
Superposition of individual S-components
Pb
Th
U
Hirschegg XXXIV ‘06
Superposition of 5 S-sequences to reproduce the Nr, pattern (100<A<240)
N=82 N=126
Th, U
r-processchronometers
Basis for detailed astrophysical parameter studies
„weak“r-process
N=50
(Thesis K. Farouqi, 2005 )
Hirschegg XXXIV ‘06
(K.-L. Kratz, B. Pfeiffer, 2005)
Calculated r-process abundances as function of neutron densities
Hirschegg XXXIV ‘06
Abundance predictions as function of nn
“weak” “main” “main”“weak”
r-process computationsfor selected elements
r-process computationsfor selected isotopes
Hirschegg XXXIV ‘06
r-Process elemental abundances
“weak” r-process
“main” r-process
Solar system Simmerer et al., 2004 CS 22892-052 Sneden et al., 2003
(see talk F. Montes)
Hirschegg XXXIV ‘06
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 -decay propertiesfission propertiesfull spectroscopy of selected “key“ waiting-point isotopes
Hirschegg XXXIV ‘06
Folded - YukawaLipkin - Nogami
≈
0+ 159 ms78Ni5028
Q = 10.45 ± 1.17 MeV (Audi ´03)
45.7% 3.5
6.6% 4.8
5.4% 5.0
32.3% 4.6
1+ g9/2 g9/2
1+ f5/2 f7/2
1+ f5/2 f7/2
g9/2 p3/2
1+ p1/2 p3/2
5.46
4.233.95
2.76
078Cu4929
78Ni5028
78Cu4929
0+ 120 ms
12.8% 3.6
51.1% 3.6
3.6% 4.9
0.5% 6.0
3.4% 5.3
27.9% 4.6
1+ f5/2 f5/2
1+ g9/2 g9/2
1+ g9/2 g9/2
1+ f5/2 f7/2
1+ f5/2 f7/2
1+ p1/2 p3/2
g9/2 p3/2
6.34
4.97
4.35
3.65
3.00
2.48
0
Lipkin - NogamiWoods - Saxon
Sn=4.24±0.57 MeV
≈
Example “future“ GSI experiment
Full understanding of shell structure of “key isotope“ 78Ni• Mass measurement ↷ Q, Sn T1/2 + Pn, n
• -spectroscopy ↷ Eℓ and log(ft) of p1/2p3/2 T1/2
Eℓ and log(ft) of g9/2g9/2 Pn
interaction
≈
≈ 9.6% 3.5 1+ f5/2 f7/2 6.93
Hirschegg XXXIV ‘06
… as an example for long “diffusion time”- from KCh Mainz → GSI Darmstadt- from experimentalist → theoretician
Hirschegg XXXIV ‘06
“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.”
Among the… Eleven Greatest Unanswered Questions of Physics (Discover Magazine, 2002)
… How were the heavy elements from Fe to U made?
Hirschegg XXXIV ‘06
Nuclear physics in the r-process
Masses (Sn)(location of the path)
-decay half-lives(progenitor abundances, process speed)
Fission rates and distributions:• n-induced• spontaneous• -delayed -delayed n-emission
branchings(final abundances)
Neutron-capture rates• for A>130 in slow freeze-out• for A<130 maybe in a “weak” r-process ?
Seed productionrates (,n, 2n, ..)
-physics ?
Hirschegg XXXIV ‘06
g 9/2
g 9/2
i13/2
i13/2
p1/2
f5/2
p 1/2
p 3/2
p3/2
f7/2
f7/2
h9/2
h 11/2
h 11/2
g 7/2g 7/2 d 3/2
d 3/2
s1/2
s 1/2
d 5/2
d 5/2
g 9/2g 9/2
f5/2f5/2
p1/2
p 1/2
h 9/2 ;f 5/2
N/Z
112
70
40
50
82
126
R - abundances Nuclear structure
Motivation:
50 82
132Sn
B. Pfeiffer et al.,Acta Phys. Polon. B27 (1996)
FK²L (Ap.J. 403 ; 1993)“..the calculated r-abundance ‘hole‘ in the A 120 region reflects ... the weakening of the shell strength ... below “
100% 70% 40% 10%
Strength of ℓ 2-Term
5.0
5.5
7.0
6.5
6.0
Sin
gle
– N
eutr
on E
nerg
ies
(Uni
ts o
f h
0)
Hirschegg XXXIV ‘06
Shell Model
QRPA(global), OXBASH, ANTOINE,...
Gamow-Teller strength functions
T½, Pxn, EQP, JQP, QP
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
Nuclear-Mass Model
FRDM, ETFSI-Q, HFB-2,...
macroscopic microscopicfinite-range folded Yukawadroplet single particle
Q, Sn, 2, s.p. wave fcts.
input for
In addition • experimental data (up to Dec. 2003)• short-range model extrapolation due to known nuclear-structure developments• inclusion of ff-strength (Gr.Th.)
Hirschegg XXXIV ‘06
R-abundance peaks and neutron-shell numbers
already B²FH (Revs. Mod. Phys. 29; 1957) C.D. Coryell (J. Chem. Educ. 38; 1961)
...still today important r-process properties to be studied experimentallyand theoretically.
K.-L. Kratz (Revs. Mod. Astr. 1; 1988)
climb up the N= 82 ladder ...A 130 “bottle neck“
total r-process duration r
“climb up the staircase“ at N=82;major waiting point nuclei;“break-through pair“ 131In, 133In;
“association with the rising side of majorpeaks in the abundance curve“
132Sn50
131In8249
133In8449
129Ag8247
128Pd8246
127Rh8245
126
127
128
129
130
131
132
133
Pn~85%
165ms278m
s
46ms(g)
r-processpath
(n,)
(n,)
(n,)135 136 137
134 135
131 132 133
130
134
158ms(m)
130Cd8248
162ms
Hirschegg XXXIV ‘06
What we knew already in 1986 ...
K.-L. Kratz et al (Z. Physik A325; 1986)
Exp. at old SC-ISOLDEwith plasma ion-sourceand dn counting
Problems:high background from
-surface ionized 130In, 130Cs-molecular ions [40Ca90Br]+
Request: SELECTIVITY !
Shell-model (QRPA; Nilsson/BCS) prediction
1.0
T1/2(GT) = 0.3 s
4.11+
2.0
g7/2, g9/2
Q = 8.0 MeV
1+
1+
1+
1+
1+
1+
1+
0
1.0
3.0
4.0
5.0
6.0
1-
IKM
z –
15
5R
(19
86
)
T1/2 = 230 ms
T1/2 = (195 ± 35) ms
Hirschegg XXXIV ‘06
Ag Cd In CsSn Sb Te I Xe
at an ISOL facility • Fast UCx target• Neutron converter• Laser ion-source• Hyperfine splitting• Isobar separation• Repeller• Chemical separation• Multi-coincidence setup
Request: Selectivity !
50 800 >105
the Ag “needle” in the Cs “haystack”
Why ?
How?
Hirschegg XXXIV ‘06
Request: Selectivity !
Laser ion-source (RILIS)
Chemically selective,three-step laser ionizationof Ag into continuum
130Cd1669 keV
130Cd 1732 keV
Laser ON
Laser OFF
130Sb1749 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 ≈ 103
Hirschegg XXXIV ‘06
The N=82 shell gap as a function of Z
The N=82 shell closure dominates the matter flow of the „main“ r-process (nn≥1023).S2n(82) – S2n(84) ↷ paired neutrons S2n(81) – S2n(83) ↷ unpaired neutrons.
Therefore request: experimental masses and more reliable model predictions
A≈130 Nr, peak
FRDM
FRDM
EFTSI-Q
EFTSI-QHFB 9
HFB 9
Groote
Groote
Hirschegg XXXIV ‘06
Hirschegg XXXIV ‘06
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:
1. 3→ 12C and2. ++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.
Hirschegg XXXIV ‘06
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/
• Expansion speed Vexp
determines process durations and r :Example: Vexp= 7500 km/s, R0= 130 km = 35 ms, r= 280 ms
Hirschegg XXXIV ‘06
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%)
Hirschegg XXXIV ‘06
Classical r-process: nn, T9= const up to break-out of (nγγn) 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!
Definition of the r-process freeze-out
Hirschegg XXXIV ‘06
Effect of neutron-capture rates on the A=130 peak
Freeze-out is fast no significant effect on A=130 peak
Hirschegg XXXIV ‘06Freeze-out is slow significant effect on A=195 peak
Effect of neutron-capture rates on the A=195 peak
Hirschegg XXXIV ‘06
Synthesizing the A=130 peak
S=196
Process duration: 146 ms
Ye Entropy S r-process duration
[ms]nn [cm-3]
at freeze outT9 [109 K]
at freeze out0,49 230 234 1,9 x1020 0,53
0,45 190 146 8,1 x1021 0,79
0,41 160 109 9,0 x1021 0,77
Hirschegg XXXIV ‘06
S=261
Pb
Th
U
not yet enough Process duration: 327 ms
Ye Entropy S r-process duration
[ms]nn [cm-3]
at freeze outT9 [109 K]
at freeze out0,49 290 412 2,0 x1021 0,33
0,45 260 327 1,5 x1022 0,41
0,41 235 213 2,9 x1022 0,42
Synthesizing the A=195 peak
Hirschegg XXXIV ‘06
Present status r-process-rich Galactic halo stars
(C. Sneden, J.J. Cowan, et al.)
Hirschegg XXXIV ‘06
Reproduce isotopic Nr,
distribution(lsq-fits; A > 80, 120)
scaled theoretical solar r-processscaled solar r-process
Nb
Zr
Y
SrMo
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
ThU
GaGe
CdSn
CS 22892-052 abundances
Hirschegg XXXIV ‘06
Cosm ochronology with Thorium
Tuning the clock w ith Uranium
Several UM P halo stars consistently show solar elem ental abundance pattern,am ong them
with elem ents between Ba and Ir,plus Pb and Th (T = 14·10 a)232 9
½
C S 22892-05217
age from average ofTh/Ba-Ir
age of the Universe
14.6 ± 3.0 Gyr
age from U /Th
(Schatz et al., 2002)
(Cowan et al., 2002)
15.0 ± 3.0 Gyr
13.8 ± 4.0 Gyr
In the m eantime, second observation of U in
age from U/Th and U,Th/3rd peakBD +17°3248
Because of shorter half-life (T = 4.5 · 10 a), U m ay yield m ore precise age.Recently, first observation of U in
½
9 238
(Cayrel et al., 2001)CS 31082-001
Ba IrPb
Th
U
Cosmo chronology with Thorium
U
Hirschegg XXXIV ‘06
• Separation and identification of fission products with the FRS
• Measuring T1/2 and Pn after implantation of nuclei in Si-stack
• 238U beam @ 750MeV/u on Pb-Target
Projectile fission produces neutron-rich nuclei
GSI-Experiment E040 (2000)
T1/2 = 296 (35)ms T1/2 = 334 (14)ms
J. Pereira, NSCL and R. Kessler, Uni Mainz
Hirschegg XXXIV ‘06
Example: recent experiment
Zr11040 70
... a new double-magic „waiting-point“ nucleus?
Beta-decay
Shell strength quenchedspherical
T½ = 88 msPn = 8 %
T½ = 14 msPn = 0.7 %
N/Zg9/2
g9/2
i13/2
i13/2
p1/2f5/2
p1/2
p3/2
p3/2
f7/2
f7/2
h9/2
h11/2
h11/2
g7/2g7/2 d3/2
d3/2
s1/2
s1/2
d5/2
d5/2
g9/2g9/2
f5/2f5/2
p1/2
p1/2
h9/2;f5/2
126
82
50
100% 70% 40% 10%
N/Z
Strength of l 2-Term
5.0
5.5
7.0
6.5
6.0
Sin
gle
– N
eutr
on E
nerg
ies
(Uni
ts o
f h
0)
112
70
40
B. Pfeiffer et al.,Acta Phys. Polon. B27 (1996)
0.85
1.6773%10%
0+ 110Zr
GT
1+ Levels
110Nb
2- 0
…
Q 9.27 MeV
Sn 3.73 MeV
110Nb
3- 0
0+ 110Zr
1+
1+
1+1+1+
1.13
5.22
6.447.047.64
Q 9.27 MeV
GT
Sn 3.21 MeV [g9/2g7/2]
99%
Exp. 5028 at NSCL/MSU; Nov. 2005; to be continued at GSI ?
Normal shell strengthstrongly deformed (2=0.31)