Explaining the large 48Ca/46Ca in the EK 1-4-1 meteorite through n-capture process

Basic charateristics / abundance patterns of the EK 1-4-1 meteorite

Astrophysical scenari to produce these abundances (-rich freeze-out, n-capt -decay process)

Need to study the N=28 closed shell : decay Neutron capture rates

Use of (d,p) transfer reaction to :Simulate (n,) capture Constraint the neutron-density value to explain the large 48Ca/46Ca abundance ratioStudy the evolution of the N=28 closed shell far from stability.

Outlooks

Did you fall tonight ? No, why ?

I heard a big ‘BANG’ !

Little story about the EK 1-4-1 inclusion of meteorite

Allende meteorite:fell in 1969weight 2tchondraneous carbideseveral CaAl-rich inclusions

EK1-4-1 inclusion :spherical shape, white colourdiametre 1cmFusion temperature1500-1900KCorrelated over-abundances in neutron rich 48Ca-50Ti-54Cr-58Fe-64Ni Underabundance of 66Zn, r process element present Nd, Sm (A~150)

48Ca/46Ca 250 (solar =53)

Mass Number A Mass Number A

64Ni48Ca

66Zn

66Zn

64Ni

K.L. Kratz et al. Proc. Della Societa Astronomica Italiana 2000

Astrophysical scenarii

S ~ T3/Ye = Z/A

SNIa –rich freeze out

28Si

weak r-process

branching point for 1021cm-1

Understand the 48Ca/46Ca 250 isotopic ratio in EK 1-4-1

-decay lifetimes Short lifetimes in the N=28 43P, 44S, and 45Cl nuclei, T1/2 (48Ar) ~500ms O. Sorlin et al. PRC 47 (1993), S. Grévy et al. PLB 594 (2004), L. Weismann et al. PRC 67 (2003)

(n,) cross sections : use (d,p) reaction in the Ar chain around N=28 see Kraussmann et al. PRC 53 (1996) for 48Ca

d

p

p

28f7/2

p3/2

p1/2

f5/2

46Ar28

Thesis work L. Gaudefroy

Usefull parameters for (n,) cross section for DC : -energy of the states-spin values-spectroscopic factors3/2-

1/2-7/2-

5/2-

(0.64)

(0.82)(0.09)

(0.23)

47ArF. Nowacki

46ArSn

0

1

2

3

4

5

E* [MeV]

CN

CN

18DC

Capture on bound states in final nucleus- cross section depends on Q, ℓ and C2S.

Neutron capture cross sections around N~28 in the Ar isotopic chain

Use of 44,46Ar (d,p) transfer reaction

CD2

380g.cm-2

40,44,46Ar 11A.MeV, 20kHz

GANIL/SPIRAL

BEAM : ~ parallel optics (size ~ 2 cm , < 2mrad)

CATS

CATS : -beam-tracking detector

- Proton emission point. resolution : ~0.6 mm

10cm.

(d,p) reactions with 40,44,46Ar beams

170°

110°

8 m

odul

esM

UST

MUST : -Si Strip detector-Proton impact localisation resolution : 1 mm

-Proton energy measurement. resolution : 50 KeV

p

SPEG

41,45,47Ar

Identification

SPEG : Energy loss spectrometer : recoil ion identification transfert-like products

CATS

MUST

CATSMUST

lab

Ep

(MeV

)Focal Plane Position (mm.)

45Ar18+45Ar17+

Beam

Stop

unbound statesin 45Ar17+

Excitation energy spectrum for 47Ar

N=28 gap : 4.47(8)MeV

p3/2

p1/2

f7/2

f5/2

47Arspec. fact.

spec. fact.

ℓ=1

ℓ=1

ℓ=3

ℓ=3

[2p1t]

3/2-

1/2-

7/2-

5/2-

(0.59)

(0.84)

(0.17)

(0.21)

47Arexp

46ArSn

0

1

2

3

4

E* [MeV]

RC18

DC

s.f

5/2-(0.46)

ℓ=1

ℓ=3

ℓ=

3

(d,p) access to E*, s.f., spins derive (n,) stellar ratesDirect capture (E1) with ℓn = 0 on p states dominatesSpeed up neutron-captures at the N=28 closed shell

Neutron capture rates on 44,46,48Ar

tn (ms)

neutron density dn

A=44

A=46

A=48

1018 1019 1020 1021 1022

0.1

1

10

100

103

104

105

t

t

106

48Ca/46Ca~250

In collab. with T.Rauscher

f7/2

p3/2

p1/2

f5/2

28

Decrease of the f and p spin-orbit splittings not predicted by mean field calculations

The N=28 gap has decreased by 330(80) keV between Ca and Ar

47Ar18

51Ti 49Ca

0

-2

-4

-6

-8

-10

f7/2

p3/2

p1/2

f5/2

?

[MeV]

28

28

20

Evolution of single particle energies at N=29

d3/2

f5/2

f7/2

Tensor monopole interaction (T. Otsuka)d3/2 –( f7/2-f5/2 )

or/and

Density dependence effect (J. Piekarewicz)

s1/2 – ( p1/2-p3/2 )

s1/2

First evidence of the tensor force in nuclei !

Conclusions and Outlooks

Use of (d,p) transfer reaction to study the N=28 shell closure :

-weakening of the N=28 shell-gap (to be continued for lighter isotones) -Vanishing of the p1/2-p3/2 spin-orbit splitting due to nuclear density term -Reduction of the f7/2 – f5/2 spin-orbit splitting due to tensor force

-Determine spectroscopic information to determine (n,)-specific orbitals (ℓ =0) with high spectroscopic factors, favors DC at N=28- Find astrophysical conditions to produce 48Ca in excess (dn ~1021cm-3).

-Outlooks: -Look at time-dependent calculations-Extent the n-capture calculations to the Ti-Cr region genitors of 58Fe, 64Ni

(only f and g valence orbitals are present)

-Other anomaleous abundances:Presolar grains SiC type X, Mo/Zr : rôle of the N=56 subshell closure?Diamond grains, Te/Xe, rôle of the N=82 shell closure ?

Collaborators :

L. Gaudefroy 1, D. Beaumel 1, Y.Blumenfeld 1, Z.Dombràdi 3, S. Fortier 1, S. Franchoo 1, M. Gélin 2, J. Gibelin 1,S. Grévy 2, F. Hammache 1, F. Ibrahim 1, K.Kemper 4, K.L. Kratz 5, S.M.Lukyanov 6,C. Monrozeau 1, L. Nalpas 7, F. Nowacki 8, A.N. Ostrowski 5, Yu.-E.Penionzhkevich 6,E. Pollaco 7, T. Rauscher9 , P. Roussel-Chomaz 2, E. Rich 1, J.A.Scarpaci 1,M.G. St. Laurent 2, D. Sohler 3, M. Stanoiu 1, E. Tryggestadt 1 and D. Verney 1

1 IPN, IN2P3-CNRS,F- 91406 Orsay Cedex, France2 GANIL, BP 55027, F-14076 Caen Cedex 5, France3 Institute of Nuclear Research, H-4001 Debrecen, Pf. 51, Hungary4 Department of Physics, Florida State University, Tallahassee,Florida 32306, USA5 Institut für Kernchemie, Universität Mainz, D-55128 Mainz, Germany6 FLNR/JINR, 141980 Dubna, Moscow region, Russia7 CEA-Saclay, DAPNIA-SPhN, F-91191 Gif sur Yvette Cedex, France8 IReS, Univ. Louis Pasteur, BP~28, F-67037 Strasbourg Cedex, France9 Dep. Of Physik and Astronomie, Universität Basel, CH4056 Switzeland

3/2-

1/2-

5/2-

7/2-

3/2-7/2-

5/2-

9/2-9/2-1/2-

(0.64)

(0.82)(0.01)

(0.09)

(0.02)(0.002)

(0.23)

47ArF. Nowacki

46ArSn

0

1

2

3

4

5

E* [MeV]

CN

CN

18DC

L. Gaudefroy, T. Rauscher

Nuclear structure of 47Ar favors s-wave Direct CaptureSpeed up the neutron captures at the N=28 closed shell(d,p) access to E*, spec. fact., spins, unbound states

s.f

Neutron capture on 46Ar

E(keV)

Origin of the deformation in the Cr isotopes

- rôle of the p-n interaction- presence of j, j-2 valence levels- mid proton shell

Large deformation in Cr:

p1/2

d5/2

g9/2

f5/2

40

E2, M2

0 4 862

protons in f7/2

proton number

N=40

34

N

time (a.u.)

E2: T1/2 ~ 1.6 s59mTi3722

shell model: F. Nowacki

fpg

Re-ordering of the levels in Ti- appearance of N=34 closed shell.

Mo, Zr anomalies in Si-C presolar grains

939290 91

91 9392

95 969492 93

94

Zr

Nb

Mo

94

1009997 98

95 9796 98 99

95 96 97 98

N=56

89 9190 92 93 9594 96 97Y

i Mo/

96M

o

s processi Zr/

94Z

r

s process

Pellin et al. Lunar Plan. Sci. (2000)

Neutron burst 1017cm-3 B. Meyer et al. Ap.J. L 540 (2000)

The g9/2-g7/2 interaction makes theN=56 subshell closure vanish at Z=42

Different patterns observed in Zr and Mo

Neutron burst

127126124 125

125 127126

129 130128126 127

128

Te

I

Xe

128

134133131 132

129 131130 132 133

129 130 131 132

123 125124 126 127 129128 130 131Sb

136135

134 135

137 138 139

133 134

132

127126124 125 128 129 130122 123Sn

N=82

i Xe/

130 X

e

i Te/

124 T

eXeTe

Te, Xe anomalies in diamond grains

r r

r

Neutron-rich scenario Influence of N=82 shell closureAbundances differ from solar r Neutron burst?

Half-lives in the Ti isotopic chain

N

t [s]

Half-lives in the Cr isotopic chain

N

t [s]

f5/2

g9/2

neutrons

f7/2

p3/2

p1/2

28

protons

(jp<)

(jp>)

(jn>)

50

d5/2

78Ni

42Si and 78Ni are mirror systems

Hints for explaining the deformation in 42Si

Doubly magic numbers originating from spin-orbit interaction

The size of the proton gaps is sensitive to the strength of the tensor monopole force

The proton and neutron gaps have ℓ=2 connections with valence states

d3/2

f7/2

neutrons

d5/2

s1/2

14

protons

(jp<)

(jp>)

(jn>)

28p3/2

42Siℓ

=2

ℓ=

2

28

Shell Model

2p1f

2s1d

2020

H.O. + L² + L.s

1g 5040

Is it due to a weakening of N=28 shell closure ?

Modification of the spin-orbit term, for which reason ?

Many hints for the onset of collectivity at N=28 far from stability, below 48Ca

The N=28 shell closure