explaining the large 48 ca/ 46 ca in the ek 1-4-1 meteorite through n-capture process
DESCRIPTION
Explaining the large 48 Ca/ 46 Ca 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 N=28 closed shell : - PowerPoint PPT PresentationTRANSCRIPT
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