Evolution of N=50 towards 78 Ni: recent inputs from experiments Workshop Espace de Structure Nucléaire Théorique Saclay 3-5 May 2010 Position of the problem : why should we worry about N=50 ? 1 N=50 shell gap evolution: salient features from experimental data 2 deeper into nuclear structure close to 78 Ni : valence space, single particle state effective sequence 3 D. Verney, IPN Orsay 0 Introduction: recent progress in experiment north north-east to 78 Ni
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Evolution of N=50 towards 78 Ni: recent inputs from experiments
Workshop Espace de Structure Nucléaire Théorique Saclay 3-5 May 2010. Evolution of N=50 towards 78 Ni: recent inputs from experiments. D. Verney, IPN Orsay. Introduction: recent progress in experiment north north-east to 78 Ni. 0. - PowerPoint PPT Presentation
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Evolution of N=50 towards 78Ni: recent inputs from experiments
Workshop Espace de Structure Nucléaire Théorique Saclay 3-5 May 2010
Position of the problem : why should we worry about N=50 ?1
N=50 shell gap evolution: salient features from experimental data2
deeper into nuclear structure close to 78Ni : valence space, single particle state effective sequence
3
D. Verney, IPN Orsay
0 Introduction: recent progress in experiment north north-east to 78Ni
0 Introduction: recent progress in experiment north north-east to 78Ni
-decay Orsay direct reaction in inverse kinematics :
Oak Ridge
DIC at Legnaro
ISOLDE laser
Experimental status in year 2010
-decay is still in the competition, good complementarities with DIC2
Fission + ISOL technique + post acceleration
BE(2)
Spectroscopic factors
DIC at Legnaro
Fusion-fission
Spontaneous fission
JYFLTRAP IGISOL
-decay Orsay
N=50 : recent experimental breakthrough
main nuclear mechanisms used :
-fragmentation of stable beams
-fission
-deep inelastic collisions
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Position of the problem : why should we worry about N=50 ?1
Why should we worry about N=50 ?
Historically from astrophysical considerations (and -decay experiments)
By Kratz et al. PRC 38 (1988)
Waiting point nucleus at N=50 80Zn
By Winger et al. PRC 36 (1987)
« »
« it’s a joke » M. Bernas, private communication (2001)
1
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ground state of 42Si N=28 is observed deformedB. Bastin et al., Phys. Rev. Lett. 99 (2007) 022503
spin-orbit origin
Why should we worry about N=50 ?
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“A full treatment of Hm shows no magicity at30Ne and 32Mg, while 34Si (or any other Si isotope)exhibits a clear shell effect. It just so happens that the fullHm reproduces the observed robustness of the SO closures,and the fragility of those of other origins. Whetherthey survive or not depends mainly on the possibility ofdeveloping quadrupole coherence in a given space.”
A.P. Zuker PRL 91 (2003)
O. Sorlin, M. Porquet Prog. Part. Nucl. Phys. 61 (2008) 602
N=50 gap extrapolation → 78Ni =3.0(5) MeV
100Sn
78Ni
from binding energies of the states below and above Z=28 and N=50
78Ni
56Ni
Z=28 gap extrapolation → 78Ni =2.5 MeV
Why should we worry about N=50 ?
44 46 48 50
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T. Otsuka et al. PRL95, 232502 (2005)
Why should we worry about N=50 ?
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extracted from J. Van de Walle et al PRC 70 (2009) 014309
Their is a N=50 shell effect with strong influence on nuclear structure close to 78Ni
Now, the real question becomes : how the shell gap associated to the N=50 magic number evolves towards 78Nior is there any evolution at all ?
N=50 shell gap evolution: prominent features from experimental data2
Evolution of the N=50 shell gap
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A Prévost et al. EPJ A 22 (2004) 391Medium/high spin states obtained from fusion/fission at the Vivitron (Euroball IV)
2 levels added : one of the two “must be” 1p-1h across N=50
T. Rza˛ca-Urban et al. PRC 76 (2007) 027302Medium/high spin states fed in 248Cm spontaneous fission
conclusion : N=50 shell gap decrease : yes
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Evolution of the N=50 shell gap
32
Y.H. Zhang et al. PRC 70 (2004) 024301Medium/high spin states fed in DIC at Legnaro (GASP)conclusion : N=50 shell gap decrease : no(same conclusion as Kamila)
(this quantity is the one traditionnally used to extract shell gaps from mass measurements)
Mass measurements (IGISOL Jyvaskyla)
Evolution of the N=50 shell gap
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Koopmans theorem :
gap in the single particle levels
50
j’
j
j’= Sn(Z,N)
but Sn(Z,N+1) is not a good prescription
for for the evaluation of j
one has to estimate j’ and jin the same
nucleus
NPA466 (1987) 189
j—j’ = Sn(Z,N) —Sn(Z,Nextr) then the good prescription becomes :
Mass measurements : what quantity is truly relevant for nuclear structure
Evolution of the N=50 shell gap
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Z
Sn(Z,N)-Sn(Z,N+1)
Sn(Z,N)-Sn(Z,Nextr)
N N+1 N+3 N+5 N+7
neutron number
using data taken from mass evaluation 2010 with kind authorization by G. Audi (AME2010 unpublished - G. Audi private communication)
d5/
2 –
g9/
2 (M
eV)
Ni Zn Ge Se Kr Sr
Duflo Zuker gap PRC59 (1999) 90Zr =4,7 MeV
Duflo Zuker gap 78Ni =5,7 MeV
gap
« rough »
« prescripted »
gap
pairi
ng g
ain(
MeV
)
neutron pairing gain = 2Sn(Z,N+1) —S2n(Z,N+2)
Ni Zn Ge Se Kr Sr
AME2010 extrapolation
Mass measurements : what quantity is truly relevant for nuclear structure
Evolution of the N=50 shell gap
loca
l min
imu
m a
t Z
=3
2
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conclusion : N=50 becomes somewhat “porous” relative to pair promotions (towards 78Ni)• what will be the result on structure? • what is the microscopic mechanism at play which could explain this local minimum ?
Zr
32
Evolution of the N=50 shell gap
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in particular : could provide a simple explanation to the Yrast structure behavior
Local minimum, not at mid distance Z=28-40
REX-ISOLDE
J. Van de Walle et al.PRL 99, 142501 (2007)
80Zn 82Ge84Se
86Kr
88Sr
90Zr
Evolution of the N=50 shell gap
and also the peculiar evolution of the E(2+) of the even-even N=50 isotones
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from -decay at ALTO
Evolution of the N=50 shell gap
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52
N=42
0.1 0.2 0.3 0.40
N=44
0.1 0.2 0.3 0.40
N=46
0.1 0.2 0.3 0.40
N=48
0.1 0.2 0.3 0.40
Ge isotopic chain
Evolution of the N=50 shell gap
and connection with collectivity
N=50
0.1 0.2 0.3 0.40
N=52
0.1 0.2 0.3 0.40
N=54
0.1 0.2 0.3 0.40
O Perru thesis Paris-Sud XI (2004) & J. Libert and M. Girod
private communicationD1S Gogny HFB calculation
GCM Bohr dynamics
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Ge
HFB + GCM (GOA)
Evolution of the N=50 shell gap
and connection with collectivity
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Collectivity close to 78Ni N=52 even-even nuclei
Z=
28 s
hell
closu
re
Z=
40 s
ubsh
ell
eff
ect
N=52
Evolution of the N=50 shell gap
and connection with collectivity
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deeper into nuclear structure close to 78Ni : valence space, single particle state effective sequence
3
Proton structure above 78Ni
K. Flanagan et al.
N=40 N=42 N=44 N=46 N=48 N=50
but already hinted at in the 80’s !!(from shell model, empirical interaction)
E (MeV)
-14,386
-13,233
-11,831
-7,121
40
f5/2
p3/2
p1/2
g9/2
Proton single particles
From Ji et Wildenthal Phys. Rev. C 38, 2849
(1988)
28
50
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Proton structure above 78Ni
shell model calculation :
Ji et Wildenthal Phys. Rev. C 38, 2849 (1988)
TBME and SP energies fitted to the data
Proton structure above 78Ni
E (MeV)
-14,386
-13,233
-11,831
-7,121
40
f5/2
p3/2
p1/2
g9/2
Proton single particles
28
50
Zn GeSe
Kr
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A. Pfeiffer et al. NPA 455 (1986) 381
Proton structure above 78Ni
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E (MeV)
-14,386
-13,233
-11,831
-7,121
40
f5/2
p3/2
p1/2
g9/2
Proton single particles
From Ji et Wildenthal Phys. Rev. C 38, 2849
(1988)
28
50
1236(9/2-)
hot subject - -decay experiment redone at ISOLDE and Oak Ridge
(same lines as us)
observed in -decay at Orsay (PARRNe)
D. Verney et al PRC 76 (2007) 054312
observed in DIC experiments at LegnaroG. De Angelis et al. NPA 787
(2007) 74c
Zn81
Sr88
Rb87
Kr86
Br85
Se84
As83
Ge82
Ga81
Zn80
Cu79
Ni78
Y89
Zr90
50
Zr91 Zr93Zr92 Zr92 Zr93 Zr94 Zr95 Zr96
Se85 Se86
As84
Ge83 Ge84
3 protons out of a 78Ni core
PARRNe
Proton structure above 78Ni
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0
200
400
600
800
1000
1200
1400
1600
1800
keV
3/2-5/2- 64 keV
0 keV
679 keV3/2-
1279 keV1/2-5/2- 1368 keV
3/2- 1897 keV
81Ga Z=31 N=50
351.1 keV
0 keV
802.8 keV
1236 keV
Experiment
empirical effective interaction : fit on a series of carefully selected states
Valence space N=50 closed & Z=28 closed (the doubly magical nature of 78Ni is assumed)The valence space is reduced to proton orbitals