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IS451-Looking at the shape transition at N=60 by safe Coulex of Sr isotopes . E.Clément -GANIL ISOLDE Workshop 2012. The n-rich nuclei between Z=37 and Z=40 present at N=60 one of the most impressive deformation change in the nuclear chart Systematic of the 2 + energy - PowerPoint PPT Presentation
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E.Clément Novembre 2011
IS451-Looking at the shape transition at N=60 by safe Coulex of Sr isotopes
E.Clément-GANILISOLDE Workshop 2012
E.Clément Novembre 2011
The n-rich nuclei between Z=37 and Z=40 present at N=60 one of the most impressive deformation change in the nuclear chart
Systematic of the 2+ energy (Raman’s formula : b2~0.17 0.4)
+ 2n
( )
S. Naimi et al., Phys. Rev. Lett. 105, 032502 (2010).
M. Albers et al., Phys. Rev. Lett. 108, 062701 (2012)
E.Clément Novembre 2011
E(0+ )
[keV
]
+ 2n
0+2
Low lying 0+ states were observed in Sr and Zr isotopes
Shape isomer in the odd-mass Sr, Zr
Shape coexistence scenario
E.Clément Novembre 2011
402p1/2
1g9/2
ll1g7/2
50
282p3/2
ll llll1f5/2 ll ll
2d5/2
3s1/2
ll ll
llll
40
1g7/2
50
K. Sieja et al PRC 79, 064310 (2009)
0+2 state created by 2p-2h excitation across Z=40
2d5/2
Beyond N=60, the p-n interaction participates to the lowering 0+
2 state and to the high collectivity of 2+
1 state.
1h11/2
E.Clément Novembre 2011
0+2 state created by 2p-2h excitation across Z=40
Beyond N=60, the p-n interaction participates to the lowering 0+
2 state and to the high collectivity of 2+
1 state. In the current valence space, need higher effective charge to reproduce collective propertiesp and n orbital from the core or higher shells.
Mean-field calculations reproduce the near spherical and highly deformed configuration away from N=60
The nuclei here are one of the best examples of the interplay between single-particle and collective modes of excitation in the nuclear matter
T. Rzaca-Urban Phys. RevC 79, 024319 (2009) – SM calculations
H. Goutte et al, CEA-Bruyère-Le-Chatel Private communication
…
²
E.Clément Novembre 2011
N=58
N=60
IS451 objectives: electromagnetic properties of the excited states in the Sr isotopes with re-accelerated beam
2011- Coulomb excitation of 98Sr
Q0s = -6 (9) efm²
B(E2↓) = 462 (11) e²fm4
2007- Coulomb excitation of 96Sr
The Electric spectroscopic Q0 is null as its B(E2) is rather large
Quasi vibrator character No quadrupole deformation
The GSB seems to be more connected to the 0+
2 than 0+3
E.Clément Novembre 2011
98Sr (T1/2 = 653 ms) has a relatively weak extraction/production rate
We choose the atomic extraction as 98A+ and relied on the in-trap b-decay of the short –lived 98Rb (T1/2 = 96 ms ) for the purification
PSB
UCx Target
Atomic extraction
HRS A= 98
98Rb (>95 % ) + 98Sr (< 5%)
Trap
EBIS
Proton beam98Rb (~2 % ) + 98Sr (~80%) +98Y (~ 9 %) 98Zr (~ 6%)
Isr ~ 6.104 pps
After several 98Rb periods : 161 + 158 ms
MINIBALL
E.Clément Novembre 2011
Trapping time: 100 ms/300ms/500ms
Several ways of sharpening the time-of-flight distribution for mass 98 were tested, without success
Preliminary conclusions
It is difficult to clearly state where the in-trap decay is the most efficient (either in the trap or in the EBIS).
The daughter nuclides delivered from the trap are not efficiently cooled.
This possibly explains why the in EBIS decay was found more efficient during the experiment of J. Van de Walle 61-62Fe from the decay of 61-62Mn (IS468).
P. Delahaye et al.
Non-decayed 98Rb b-decay product
The peak disappear after a sufficiently long trapping time
E.Clément Novembre 2011
37 Cl10+ 6
1 X (short-
lived)
98Rb :102 ms98 Sr : 6
53 ms
98Y98Zr : 30 sec.
98mRb : 96 ms
0+ (4,5) :2 se
c.
(0- ) :
548 ms
98Rb
98Sr
98Y
98Zr
98Nb
Beam composition after post-acceleration
DE measurement at MINIBALL
Energy loss (MeV)
15N
60Ni
64Zn
83Kr
38Ar
p off Beam Gate close EBIS-contamination
p off Beam Gate open Long lived from target
p on Beam Gate open Short lived from target
? ?
E.Clément Novembre 2011
We used 2 Target : 208Pb & 60Ni Clean kinematic matrix Doppler corrected, particle-g prompt gated
98Sr : Coulomb excitation results
208Pb target
60Ni target
Target excitation
E.Clément Novembre 2011
115 keV
4+
6+
Gated on the 2+ decay
g-g matrix Many transitions are in coincidence
E.Clément Novembre 2011
(115)
(319)
Other unknown transitions might belong to 98Rb
Gate on 115 keV
Gate on 319 keV
E.Clément Novembre 2011
Conclusion
oWe successfully performed the Coulomb excitation of 96-98Sr beams and many transitions have been observed in 98Sr
oWe used the in-trap and in-ebis b-decay
oThe effect of different configurations of the trapping and breeding time are not understood
oWe observed new transitions in 98Sr analyzed using g-g coincidences after coulomb excitation of a RIB.
oWe might have identified excited states in 98Rb
o E2-M1 electromagnetic matrix elements analysis on-going
o Next step : Zr beams and transfer reaction on Sr
E.Clément Novembre 2011
AGATA@GANIL
The GANIL facility will host the European AGATA germanium array during 2014 and 2015
Gamma-ray spectroscopy of very neutron-rich nuclei populated in Deep Inelastic collisions or induced fission
Spectroscopy of heavy elements towards SHE and N=Z nuclei
Spectroscopy using existing and new SPIRAL1 beams
Submission of the LoI by February 8th, 2013
AGATA@GANIL Workshop GANIL, 18-20 February, 2013
http://pro.ganil-spiral2.eu/events/cw/agataws.
E.Clément Novembre 2011
96Rb (N=59)
165
999451 259
380
98Rb ?? (N=61)
No excited states are known in 98Rb Level scheme very similar to 96Rb
No coincidence with known transition in 98Sr
98Sr : Coulomb excitation results g-g analysis
E.Clément Novembre 2011
Pb
t = 4 ns ~ t.o.f
After DC
t.o.f is longer and longer
98Sr : Coulomb excitation resultsPlunger type analysis
E.Clément Novembre 2011
Path = t.o.f
t = 2.9 (3) ns (4.0(1) ns)
Not yet fully understood the difference
Geometrical effect ( cluster) ?
Influence of higher lying states ?
98Sr : Coulomb excitation resultsPlunger type analysis
Decay curve
E.Clément Novembre 2011
115
319(0+,3-)m
(2+,5-)
144
98Sr : Coulomb excitation resultsPlunger type analysis
Cos y Cos y
EDc
Isomeric state ! t = 1.2 (3) ns
E.Clément Novembre 2011
First Sr beam at REX-ISOLDE
We choose the molecular extraction as 96Sr19F+ to not suffer from the Rb contamination
PSB
UCx Target
7 to 1.3 105
96Sr19F+/C
Molecular extraction
HRS A= 115
96Rb
( Trap HS ) …. off
EBIS
Separator
115In
Proton beam
A/Q = 4.17
Pure 96Sr23+ REX-beam2.87 MeV/u 1 to 0.5 ~104 pps
2007 – Coulomb excitation of 96Sr