Towards 78 Ni: In-beam γ-ray spectroscopy of the exotic nuclei close to N=50 IPN Orsay: D. Verney, M. Niikura , F. Aziez, S. Franchoo, F. Ibrahim, F. Le Blanc, I. Matea, I. Stefan CSNSM Orsay: A. Korichi GANIL Caen: L. Càceres, E. Clément, G. De France, S. Grévy, O. Solin IPHC Strasbourg: F. Didierjean, G. Duchene LPSC Grenoble: G. Simpson LNL-INFN Legnaro G. De Angelis, E. Sahin, J.J. Valiente Dobon
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Towards 78 Ni - WebDocs < Linux < GSI Wikiwolle/PreSPEC/Workshops/Ist… · · 2010-05-066th May 2010 AGATA Istanbul workshop Proposed experimental setup 11 Zr90 Zr91 Y89 Sr88 Rb87
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Towards 78Ni:In-beam γ-ray spectroscopy of the exotic
nuclei close to N=50
IPN Orsay:D. Verney, M. Niikura, F. Aziez, S. Franchoo, F. Ibrahim, F. Le Blanc, I. Matea, I. Stefan
CSNSM Orsay:A. Korichi
GANIL Caen:L. Càceres, E. Clément, G. De France, S. Grévy, O. Solin
IPHC Strasbourg:F. Didierjean, G. Duchene
LPSC Grenoble:G. Simpson
LNL-INFN LegnaroG. De Angelis, E. Sahin, J.J. Valiente Dobon
AGATA Istanbul workshop6th May 2010
Physics case: Study of shell structure above 78Ni
2
Zr90 Zr91
Y89
Sr88
Rb87
Kr86
Br85
Se84
As83
Ge82
Ga81
Zn80
Cu79
Ni78
Zn78Zn77Zn76
Ni74 Ni76Ni75
Ge83
As84
Se85 Se86
Ge84
Se80 Se82
Br81
Kr82 Kr84Kr83
Rb85
Sr86 Sr87
Zn79
Ni76
Cu75
Se84
50
28
Zr92 Zr94 Zr96
Known p
art of
the
valen
ce sp
ace
Unknown p
art of t
he
valen
ce space
Proton single particles
d5/2 d3/2s1/2 g7/2
Neutron single particles
f5/2
p3/2
p1/2
g9/2
OK
OK
?
π-ν Residual
interaction
• Is 78Ni a good core? Persistence of Z=28 and N=50, pair promotions from the lower shells
• What is the nature of valence space which opens up just above ? single particle sequence
AGATA Istanbul workshop6th May 2010
Is 78Ni good core?
3
Probably yes...
• O. Sorlin, M. Porquet Prog. Part. Nucl. Phys. 61 (2008) 602
from binding energies of the states blow and above Z=28 and N=50
N=50 gap extrapolation → 78Ni =3.0(5) MeV
100Sn
78Ni
78Ni
56Ni
Z=28 gap extrapolation → 78Ni =2.5 MeV
• from B(E2) measurement in 80Zn (REX-ISOLDE)J. Van de Walle et al. PRC 79, 014309 (2009)«No direct evidence is found for an enhanced Z = 28 core polarization, but the larger proton effective charge needed in the SMI calculations to describe N = 50 isotones with Z < 40 indicate a larger proton core polarization for these isotopes. No evidence is found for breaking of the N = 50 shell gap. »
• from Yrast structure studies from DIC experiments (Legnaro) down to 82Ge Y. H. Zhang et al. PRC 70, 024301 (2004) and subsequent studies E. Sahin et al.« The generally good agreement obtained between calculated and measured level energies in all the cases considered is taken as an argument for the proper description of such semi magic nuclei within the shell-model framework and therefore of the persistence of the N=50 closed shell down to Z=32. »
• from β-decay studies down to 81Ga (Orsay)O. Perru et al. Eur. Phys. J. A 28, 307 (2006)D. Verney et al. PRC 76, 054312 (2007)
• from mass measurements down to 80Zn (IGISOL Jyvaskyla)J. Hakala et al. PRL 101, 052502 (2008)« The data indicates the persistence of this gap towards Ni (Z =28) with an observed minimum at Z=32. »
maybe not...
AGATA Istanbul workshop6th May 2010
N=50 shell gap has local minimum at Ge
4
Two neutron separation energyΔ=S2n(52)-S2n(50)
↓N=50 shell gap
Local minimum at Ge (Z=32)
J. Hakala et al. PRL 101, 052502 (2008)
AGATA Istanbul workshop6th May 2010
Increasing collectivity toward N=50 in Ge isotope
5
Ge isotopes
Sphericalvibration
“γ-soft”nucleus
Triaxial rotationProlate
vibration
N=48
0.1 0.2 0.3 0.40
80Ge
0.1 0.2 0.3 0.40
N=4678Ge
0.1 0.2 0.3 0.40
N=4476Ge
0.1 0.2 0.3 0.40
N=4274Ge
N=50
“γ-soft”nucleus
HFB D1S Gogny + GCM:O. Perru, J. Libert and D. Girod
AGATA Istanbul workshop6th May 2010
What is the nature of valence space above 78Ni?
6
E (MeV)
0.00
1.00
2.453.04
82Neutron single particles
T.A. Hughes, Phys. Rev. 181, 1586 (1969)
d5/2
d3/2
s1/2
g7/2
50
in 89Sr
? h11/2
Shell model calc. with 78Ni coreK. Sieja et al. PRC 79, 064310 (2009)
Duflo Zuker
PRC 59, R2347 (1999)
AGATA Istanbul workshop6th May 2010
0
500
1000
1500
2000
2500
3000
Exci
tatio
n en
ergy
[keV
]
7
N=51 isotone systematic
89Sr(Z=38)
87Kr(Z=36)
85Se(Z=34)
83Ge(Z=32)
81Zn(Z=30)
Zr90 Zr91
Y89
Sr88
Rb87
Kr86
Br85
Se84
As83
Ge82
Ga81
Zn80
Cu79
Ni78
Ge83
As84
Se85
Sr87
Zn79
Ni77
50
Zn81
Kr87
Sr89
7/2+
7/2+
1/2+
5/2+
3/2+ 50
d5/2s1/2d3/2g7/2
g9/2p1/2
2+ d3/2
or g7/2?
79Ni(Z=28)
?
AGATA Istanbul workshop6th May 2010 8
0
500
1000
1500
2000
Exci
tatio
n en
ergy
[keV
]
N=49 isotone systematics
87Sr(Z=38)
85Kr(Z=36)
83Se(Z=34)
81Ge(Z=32)
79Zn(Z=30)
Zr90 Zr91
Y89
Sr88
Rb87
Kr86
Br85
Se84
As83
Ge82
Ga81
Zn80
Cu79
Ni78
Ge83
As84
Se85
Sr87
Zn79
Ni77
50
Kr85
Se83
Ge81
1/2+
5/2+
1/2-
9/2+
3/2+
50
d5/2s1/2d3/2g7/2
g9/2p1/2
77Ni(Z=28)
R.A.Meyer et al., PRC 25 (1982) 682
??
AGATA Istanbul workshop6th May 2010 9
Valence space for proton in west part of 78Ni
T. Otsuka et al. PRL95, 232502 (2005)
K. Flanagan et al., PRL 103, 142501 (2009)
Zr90 Zr91
Y89
Sr88
Rb87
Kr86
Br85
Se84
As83
Ge82
Ga81
Zn80
Cu79
Ni78
Ge83
As84
Sr87
Zn79
Ni77
50
Cu77Cu76Cu75Cu74Cu73Cu72Cu71Cu70Cu69 Cu78
AGATA Istanbul workshop6th May 2010
Valence space for proton in north part of 78Ni
10
Zr90 Zr91
Y89
Sr88
Rb87
Kr86
Br85
Se84
As83
Ge82
Ga81
Zn80
Cu79
Ni78
Ge83
As84
Sr87
Zn79
Ni77
50
the observed structure of the odd-proton N=50 isotones should only (and naturally) reflects the change of the Fermi level to be checked experimentally
From Ji et Wildenthal Phys. Rev. C 38, 2849 (1988)
• 83As beam (220 MeV/u, 2.5x104 pps)• Be target (2650 mg/cm2)• 15% efficiency for AGATA• all products through 1st to g.s. transition
AGATA Istanbul workshop6th May 2010
Summary
We propose to perform the in-beam gamma-ray spectroscopy of very neutron-rich nuclei around N=50 towards 78Ni using the secondary fragmentation reaction of a 83As (Z=33, N=50) beam with FRS + AGATA + LYCCA.
Physics interest
• 78Ni can be considered as a good core for shell model?
• increasing collectivity across N=50 (2+, 4+ sequence)
• shell structure, order of orbit, π-ν interaction
• proton shell seems to be understood by tenser interaction (cf. Cu isotope)
• inversion of g.s. spin from 5/2- to 3/2- between 85Ba and 83As
• decreasing single-particle energy space between νs1/2 and νd5/2