1. In-beam and isomer spectroscopy in the third island of inversion at EXOGAM+VAMOS
E.Clément (GANIL)

2. Weakness of the N=40 shell gap
M. Bernas et al., PLB 113 (1982)
R.Broda et al., PRL 74 (1995)
O.Sorlin et al.,PRL 88 (2002)
C. Guénaut et al., PRC 75 (2007)
68Ni
69Cu
68Cu
67Co
67Ni
70Zn
70Cu
69Ni
66Co
68Co
66Fe
65Mn
65Fe
67Fe
65Co
64Fe
64Mn
63Mn
Presence of single particle,
collective and core-coupled
states.
I.Stefanescu et al., PRL 100 (2008)
70Ni
Core polarization
O. Perru et al., PRL 96 (2006)
Presence of core coupled states : Fe-like and Ni-like
D.Pauwels et al., PRC 79 (2009)
A.Dijon et al, PRC 83 (2011)
The mass region around 68Ni remains a real puzzle… It is now established that 68Ni presents some characteristics of a doubly magic nuclei but in the other hand, the N=40 subshell closure appears as a rather open shell. Therefore, interaction between valence proton and this open neutron shell leads to an abrupt evolution of the collectivity. For example, above 68Ni, in copper isotopes, single particle, collectifs and core-coupled states are present. Below 68Ni, in iron isotopes, an onset of deformation from N=36 toward N=40 has been confirmed involving neutron intruder orbitals. In n-rich odd mass Co which are very closed to this border of deformation, a presence of core coupled state has been also made in evidence. In this experiment, we have investigated the core coupled states in this region. Finally at Z=28, as I will show, only few information are known on the proton states.
Onset of deformation
in Fe isotopes
J.Ljungvall et al., PRC 81 (2010)
W.Rother et al., PRL 106 (2011)

3. Single particle state by B(E2) measurement
68Ni
69Cu
68Cu
67Co
67Ni
70Zn
70Cu
69Ni
66Co
68Co
66Fe
65Mn
70Ni
65Fe
69Co
67Fe
69Cu : p(2p-1h)
Single particle state by B(E2) measurement
(I.Stefanescu et al., PRL 100 (2008) )
68Ni must present a p(2p-2h)
intruder state with
E(p(2p-2h) )=E(p(2p-1h) )+E(p(1p-2h))
0+ state
(D.Pauwels et al . PRC 82 (2010))
67Co : p(1p-2h)
Shape isomer at N=40 : proton intruder state p (p1/2)+1 (D.Pauwels et al . PRC 78 (2008))
Indeed , around 68Ni, proton intruder states have been identified. In 69Cu, for example, a single particle state with 2p 1 hole configuration has been mesured and in 67Co,the presence of of shape isomer bellow 500 keV which have 1p-2h configuration has been measured. And more recently, it has been made in evidence a possibility that the ground state in 66Co could be also based on a proton intruder config. So, it must be possible to have a proton intruder state at low excitation energy that could be isomeric or not and it is why we decide to measure the delay and prompt gamma rays.
p(2p-2h) intruder states at low energy  π-ν residual energy.

4. ∆M/M=1.2% ∆Z/Z =1.1% 2 Ge Eurogam phase 1 + No Dipole 2 Ge EXOGAM Sed2
6.33 A MeV
70Zn target
Sed1
Sed2
11 EXOGAM
Ge detectors
No Dipole
45°
Ionisation chamber
(3 pads) + 4 Si detectors
2 Ge Eurogam
phase 1 +
2 Ge EXOGAM
detectors
VAMOS Spectrometer
MWPC Q2 Q1
In this experiment, I will present the preliminary results of a second experiment which aimed to perform prompt and delayed gamma rays spectroscopy using a specific configuration of the VAMOS spectrometer so-called the solenoid mode.
In this experiment, an Uranium beam at 6.33 MeV/A impinge a 70Zn target. The gamma rays emitted at the target point were measured in the Exogam Ge detector and the target like reaction product are refocalized and identified in the VAMOS spectrometer. No Brho analysis is performed in this configuration. At the focal plane of the VAMOS spectrometer, four germanium detector are used to measure delayed gamma rays. We have achieved very good Z and M resolution allowing an unique identification for mass up to 80.
Z identification
∆Z/Z =1.1%
∆M/M=1.2%
counts
M identification

5. PRELIMINARY 168(1) keV 68Ni 69Cu 67Ni 69Ni Prompt Isomer Isomer
A. Dijon et al, to be submitted very soon …
Prompt
168(1) keV
T1/2= /-50 ns
Isomer
69Cu
67Ni
69Ni
68Ni
Isomer
As a main result, we observed for the first time the presence of new isomer transition at 168 keV. We measured a lifetime of 157 ns. Weiskpoff estimate favours an E2 decay leading to a low B(E2) underlining a single particle transition.
PRELIMINARY

6. Gated on transitions in 67Ni
Gated on the 168 keV transition
 Observed just for Z=28
Gated on transitions in 69Cu
Gated on transitions in 69Ni

7. 168(1) keV 68Ni 69Cu 67Ni 69Ni Prompt Isomer
A. Dijon et al, to be submitted very soon …
Prompt
168(1) keV
T1/2= /-50 ns
Isomer
69Cu
67Ni
69Ni
68Ni
As a main result, we observed for the first time the presence of new isomer transition at 168 keV. We measured a lifetime of 157 ns. Weiskpoff estimate favours an E2 decay leading to a low B(E2) underlining a single particle transition.

8. Transitions Half-life E1 0.1 ps E2 300 ns M1 6 ps M2 20 μs
Prompt
Prompt
168(1) keV
T1/2= /-50 ns
Isomer
69Cu
67Ni
69Ni
68Ni
Compatible with
small B(E2) value
As a main result, we observed for the first time the presence of new isomer transition at 168 keV. We measured a lifetime of 157 ns. Weiskpoff estimate favours an E2 decay leading to a low B(E2) underlining a single particle transition.

9. Shape Coexistence scenario
4+1
5-2
5-1
2+2
0+3
π(f7/2)-2
0+m2
* 70Zn(14C,16O)68Ni M. Girod et al PRC 37 (1988), at the Orsay Tandem
2+1
0+1
π(f7/2)-2 (p3/2)+1
0+g.s
66Fe 2+
B(E2) =21 W.u
575
π(f7/2)-2
Deformed
W.Rother et al.,
PRL 106 (2011)
(1/2-m)
(7/2-)g.s
67Co
491
Shape isomer
D.Pauwels et al., PRC 78 (2008) 0+
68Ni
Remarkable agreement with the predited position from the p(1p-2h) in 67Co and p(2p-1h) in 69Cu
 p(2p-2h) state
 Suggest the microscopical configuration
D. Pauwels et al, PRC 82, (2010)
Shape Coexistence scenario

10. Correlation energy : -30.9 MeV Q² = 4520 e²fm4  b ~ 0.4 …
8+1
Correlation energy : MeV
Q² = 4520 e²fm4  b ~ 0.4 …
0+m2
LSSM – LPNS : F. Nowacki, K. Sieja
for A. Dijon et al, to be submitted very soon …
B(E2)cal= 0.9 W.u
Exp : < 1.4 W.u (E0?)
2+1
0+1
g9/2
d5/2
p1/2
f5/2
p3/2
f7/2
Calculated GS
0+1
0+2
neutron
proton
Q² = 1579 e²fm4  b ~ 0.24 0+
Occupation number
Correlation energy : -7.6 MeV
Q² = 899 e²fm4  b ~ 0.18
π(f7/2)-2

11. n p p × Not present in the ph-RPA calculations × Not present in the
68Ni
HFB-D1S p
fully consistent QRPA calculations with D1S interaction
M. Martini, S. Péru for A. Dijon et al, to be submitted very soon …

12. The solenoid mode in this experiment shows interesting results:
Prompt and delayed gamma rays in coincidence
Lifetime of isomer
A new isomer has been identified in 68Ni
Interpreted as a 2p-2h proton intruder superdeformed state across the Z=28 major shell closure
In agreement with SM calculations using the recent LPNS interaction
In agreement with QRPA calculations
Similar microscopic configuration with 67mCo and 66Fe
 Shape coexistence in 68Ni
So, to conclude, the preliminary results of this experiment seems to be hopeful and show a possibility of a new 0+ excited state in 68Ni with a pure proton configuration. New gamma prompt are also observed in iron isotopes but also in others nuclei populated in this experiment.

13. Collaboration

15. S.M. Lenzi, F.Nowacki, A.Poves and K.Sieja, PRC 82 (2010)
K.Heyde and J.L. Woods,
Rev.Mod.Phys (in press)
F.Nowacki and K.Sieja for A. Dijon et al (2011)
Correlation energy : -7.6 MeV
Q² = 899 e²fm4  b ~ 0.18
Correlation energy : MeV
Q² = 4520 e²fm4  b ~ 0.4
D.Pauwels et al., PRC 82 (2010)
-3.8 MeV

16. A 0+ state ? : Looking at the past …
M. Girod et al PRC 37 (1988)
M. Bernas et al PLB B113,(1982)
Remember, at this time the 2+ at 2033 keV was not known : the 2.20(3) MeV state interpreted as a the 2+1 state

17. A 0+ state ? : Looking at the past …
M. Girod et al PRC 37 (1988)