AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Deformation in N=40 nuclei G....
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Transcript of AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010 G. Duchêne Deformation in N=40 nuclei G....
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
G. D
uch
ên
e
In2p3
Deformation in N=40 nuclei
G. Duchêne , R. Lozeva, C. Beck, D. Curien, F. Didierjean, Ch. Finck, F. Nowacki, K. Sieja
IPHC StrasbourgC. Domingo-Pardo, J. Gerl and the GSI group
GSI DarmstadtD. Verney, F.Azaiez, S. Franchoo, F. Ibrahim, F. Le Blanc, I. Matea,
M. Niikura, I. StefanIPN Orsay
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
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In2p3
Deformation in Fe and Cr nucleiE. Caurier et al., Eur. Phys. J A15 (2002) 145
Fe
Cr Cr
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
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68Ni
Is 68Ni a magic nucleus ? Increase of the 21
+ excitation energy Reduction of the B(E2) value
No pronounced irregularity in the 2-neutron separation energy
Strong 2p-2h component -> excitation of a neutron pair into g9/2 orbital
Major part of the B(E2) strength around 5 MeV
Deformation in 68Ni 68Ni gs is spherical (Gaudefroy et al.,
Phys. Rev. C80 (2009) 064313) Main 01
+ state configuration is 4p-4h Does not generate much
deformation
K. Langanke et al., Phys. Rev. C67 (2003) 044314
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
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In2p3
In the vicinity of 68Ni
67Co Collective 1p-2h proton intruder First excited ½- state with large
quadrupole deformation β ~ 0.25-0.4D. Pauwels et al., Phys. Rev. C 78, 041307(R)
(2009)
69Cu Measured magnetic moment of 13/2+
state Considerable proton excitations
across the Z=28 proton gap Deviate from sphericityG. Georgiev et al., J. Phys. G: Nucl. Part. Phys.
28, 2993 (2002)
70Zn Given as a γ-soft nucleus (Gaudefroy et
al., Phys. Rev. C80 (2009) 064313)
Hunt for deformation with np-nh
configurations (n=6, 8) at higher
excitation energy
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
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In2p3
Shell-model calculations
Valence space 40
20Ca20 core π: f7/2 + fp shell υ: f7/2 frozen + fp shell (p3/2 frozen)+ g9/2 + d5/2
68Ni: 8p-8h excitations 70Zn: 6p-6h excitations
Huge matrices to diagonalise~(500 106)² to more than (109)²
Several days calculation
Results 68Ni 8p-8h config:
B(E2)down ~ 690 e²fm4
Q2 = -49 e.fm²
β2 ~ 0.32E* ~ 13 MeV
6p-6h config:B(E2)down ~ 190 e²fm4
Less deformation drivingE* ~ 10 MeV
70Zn 6p-6h config:B(E2)down ~ 695 e²fm4
Q2 = -48 e.fm²
β2 ~ 0.32E* ~ 10 MeV
All configurations are spread over many states when configuration mixing is allowed !
Mean field calculation in the β-γ plan
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
G. D
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In2p3
Angular momentum and particle rates
High-angular momentum states feeding Several nucleon knock-out lead to « high-
spin » transfers 8+ fed ~10 time less than 2+ state Hypothesis: deformed structure feeding of
10% at 8 ħ
Nuclei production rate Primary beam: 76Ge -> Imax = 3 108 p/s Primary Be/Nb target of 2.5 g/cm² Al degrader of 1.5 g/cm² Intermediate fragments: 73Ga or 72Zn Rates calculations (slits cuts in S1, S3, S4)
AGATA Lycca
105 Hz/wire
104 Hz
Primary beam (p/s)
Intermediate
fragment
Transmissio
n
S4 rate (p/s)
ReactionFinal
nucleus
Production rate
(p/s)
7 106 p/s 7331Ga 30% 104
fragmentation
6828Ni 0.3
1p-2n knock-out
7030Zn 18
3 107 p/s 7230Zn 42% 104
fragmentation
6828Ni 2.5
2n knock-out 7030Zn 35
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
G. D
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In2p3
Gamma-ray statistics
S’2 geometry Full configuration: 10TC + 5DC -> 17% Min. configuration: 5TC + 3DC -> 9%
Intermediate fragment 72Zn; 1.5 MeV gamma ray
Experiment duration: 7 days
Projectile
Nucleus of
interest
AGATA config.
γ-rate (min-1)
Total counts singles
in 7 days
γ γ -rate (min-1)
Total counts doubles
in 7 days
72Zn
68Ni2.5 p/s
Full 0.19 1900 0.024 244
Min 0.10 1000 0.0068 69
70Zn35 p/s
Full 2.66 26600 0.34 3400
Min 1.40 14000 0.095 950
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
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In2p3
Ni-Zn-Ge
Gaudefroy et al., Phys. Rev. C80 (2009) 064313
J. Van de Walle et al., Phys. Rev. Lett.99 (2007) 142501
AGATA Physics Workshop Istanbul, Turkey May 4-7, 2010
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In2p3
Tensor force
Attractive between spin-flip orbitals
Attractive interaction πf5/2-νd5/2
Relaxed when removing protons from πf5/2 orbital
Excitation energy of νs1/2 state apparently decreases vs νd5/2 state
π ν
f7/2
p3/2
f5/2
p1/2
g9/2
d5/2
s1/2
g7/2
j+1/2
j-1/2