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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 (a-rich freeze-out,
n-capt b-decay process) Need to study the N28
closed shell b decay Neutron capture
rates Use of (d,p) transfer reaction to
Simulate (n,g) capture Constraint the
neutron-density value to explain the large
48Ca/46Ca abundance ratio Study the evolution of
the N28 closed shell far from stability.
Outlooks
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Little story about the EK 1-4-1 inclusion of
meteorite
I heard a big BANG !
Did you fall tonight ?
Allende meteorite fell in 1969 weight
2t chondraneous carbide several CaAl-rich
inclusions
EK1-4-1 inclusion spherical shape, white
colour diametre 1cm Fusion temperature1500-1900K C
orrelated over-abundances in neutron rich
48Ca-50Ti-54Cr-58Fe-64Ni Underabundance of 66Zn,
r process element present Nd, Sm (A150)
48Ca/46Ca ? 250 (solar 53)
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Understand the 48Ca/46Ca ? 250 isotopic ratio in
EK 1-4-1
b-decay lifetimes Short lifetimes in the N28
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,g) cross sections use (d,p) reaction in the
Ar chain around N28 see Kraussmann et al. PRC
53 (1996) for 48Ca
branching point for 1021cm-1
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Neutron capture cross sections around N28 in the
Ar isotopic chain
E MeV
Use of 44,46Ar (d,p) transfer reaction
ltsgtCN
5
CN
Sn
46Ar
4
18
DC
3
5/2-
(0.23)
Usefull parameters for (n,g) cross section for
DC -energy of the states -spin
values -spectroscopic factors
2
(0.09)
7/2-
(0.82)
1/2-
1
(0.64)
3/2-
0
47Ar F. Nowacki
Capture on bound states in final nucleus - cross
section depends on Q, l and C2S.
Thesis work L. Gaudefroy
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(d,p) reactions with 40,44,46Ar beams
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In collab. with T.Rauscher
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First evidence of the tensor force in nuclei !
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Conclusions and Outlooks

• Use of (d,p) transfer reaction to study the N28
  shell closure
• weakening of the N28 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,g)
• specific orbitals (l 0) with high spectroscopic
  factors, favors DC at N28
• 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
  N56 subshell closure?
• Diamond grains, Te/Xe, rôle of the N82 shell
  closure ?

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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, France 2 GANIL,
BP 55027, F-14076 Caen Cedex 5, France 3
Institute of Nuclear Research, H-4001 Debrecen,
Pf. 51, Hungary 4 Department of Physics, Florida
State University, Tallahassee,Florida 32306,
USA 5 Institut für Kernchemie, Universität Mainz,
D-55128 Mainz, Germany 6 FLNR/JINR, 141980 Dubna,
Moscow region, Russia 7 CEA-Saclay, DAPNIA-SPhN,
F-91191 Gif sur Yvette Cedex, France 8 IReS,
Univ. Louis Pasteur, BP28, F-67037 Strasbourg
Cedex, France 9 Dep. Of Physik and Astronomie,
Universität Basel, CH4056 Switzeland
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Neutron capture on 46Ar
E MeV
ltsgtCN
5
CN
Sn
46Ar
4
18
1/2-
DC
9/2-
9/2-
3
(0.23)
5/2-
(0.002)
7/2-
2
3/2-
(0.02)
(0.09)
7/2-
(0.82)
1/2-
(0.01)
5/2-
1
(0.64)
3/2-
0
47Ar F. Nowacki
s.f
L. Gaudefroy, T. Rauscher
Nuclear structure of 47Ar favors s-wave Direct
Capture Speed up the neutron captures at the N28
closed shell (d,p) access to E, spec. fact.,
spins, unbound states
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Origin of the deformation in the Cr isotopes
Ng
Large deformation in Cr
59mTi37
E2 T1/2 1.6 ms
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• rôle of the p-n interaction
• presence of j, j-2 valence levels
• mid proton shell

Re-ordering of the levels in Ti - appearance of
N34 closed shell.
time (a.u.)
E(keV)
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Mo, Zr anomalies in Si-C presolar grains
Pellin et al. Lunar Plan. Sci. (2000)
Neutron burst
iZr/94Zr
iMo/96Mo
s process
s process
100
99
97
98
95
96
94
92
93
Mo

• Neutron burst 1017cm-3
• B. Meyer et al. Ap.J. L 540 (2000)
• The pg9/2-ng7/2 interaction makes the
• N56 subshell closure vanish at Z42
• Different patterns observed in Zr and Mo

Nb
91
93
92
94
95
97
96
98
99
Zr
93
92
90
91
94
97
98
95
96
89
91
90
92
93
95
94
Y
96
97
N56
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Te, Xe anomalies in diamond grains
r
r
r
Neutron-rich scenario Influence of N82 shell
closure Abundances differ from solar r ? Neutron
burst?
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Half-lives in the Ti isotopic chain
Nb
t s
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Half-lives in the Cr isotopic chain
Nb
t s
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Many hints for the onset of collectivity at N28
far from stability, below 48Ca
The N28 shell closure