Hirschegg XXXIV ‘06 - Institut für Kernchemie, Univ. Mainz, Germany - HGF VISTARS, Germany - Department Of Physics, Univ. of Notre Dame, USA Karl-Ludwig

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


-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


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


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)


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


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


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 paths for nn=1020 and 1023

(T1/2 exp. : 28Ni – 31Ga, 36Kr, 37Rb,47Ag – 51Sb)

nn=1023

nn=1020


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



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)


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 !


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


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 ‼


Effects of nuclear masses on Nr, fits

T1/2+Pn and all astro-parameters kept constant !


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


Synthesizing selected mass region

S=196 + 261 + 280

Superposition of individual S-components

Pb

Th

U


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 )


(K.-L. Kratz, B. Pfeiffer, 2005)

Calculated r-process abundances as function of neutron densities


Abundance predictions as function of nn

“weak” “main” “main”“weak”

r-process computationsfor selected elements

r-process computationsfor selected isotopes


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)


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


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


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


“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?


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 ?


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)


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.)


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


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


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?


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


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



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.


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


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%)


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


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


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


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


Present status r-process-rich Galactic halo stars

(C. Sneden, J.J. Cowan, et al.)


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


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


• 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


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)

Documents

Hirschegg XXXIV ‘06 - Institut für Kernchemie, Univ. Mainz, Germany - HGF VISTARS, Germany - Department Of Physics, Univ. of Notre Dame, USA Karl-Ludwig