Transcript Document

Coulomb excitation of the neutron-rich Cu
isotopes and isomers using RILIS
Irina Stefanescu1, O. Ivanov1, J. Van de Walle1, N. Patronis1, D. Pauwels1,
T. E. Cocolios1, N. Bree1, M. Huyse1, P. Van Duppen1
G. Georgiev2, T. Kröll3, P. Maierbeck3, A. Blazhev4, N. Warr4, S. Franchoo5, J. Iwanicki6,
P. Napiorkowski6, K. Wrzosek6, D. Balabanski7, K. Gladnishki7, G. Rainovski7,
G.
Lo Bianco8, N. Blasi8, A. Lagoyannis9, T. Konstantinopoulos9, A. Ekström10
1IKS,
KU Leuven
2CSNSM Orsay, France
3TU München, Germany
4IKP Köln, Germany
5IPN Orsay, France
6Heavy Ion Laboratory, Warsaw University, Poland
7University of Sofia, Bulgaria
8Universita di Camerino, Italy
9National Research Center Demokritos, Greece
10Lund University, Sweden
Funded by IAP Belgium, BMBF, EURONS
Beyond 68Ni by Coulomb excitation with RIBs
g9/2
40
p1/2
f5/2
p3/2
ll
llllll
llll
28
28
protons
neutrons
N=40
llllllll f7/2 llllllll
B(E2;2+0+) by Coulex
 70Ni (68Ni+2n) and 70Zn (68Ni+2p) show large
collectivity at low excitation energies;
+2p
68Ni
+2n
 tensor force: shifts and re-ordering of the
single-particle orbits  erosion of the Z=28 and
N=40 gaps.
(T. Otsuka, PRL 95, 232502 (2005)).
N=50
ll
ll
Beyond 68Ni by Coulomb excitation with RIBs
l
28
p1/2
f5/2
p3/2
ll
40
ll
llllll
llll
28
protons
neutrons
N=40
llllllll f7/2 llllllll
B(E2;2+0+) by Coulex
 n-rich Cu isotopes provide an excellent means for testing the proton-neutron
residual interaction in this mass -region;
 n-rich Cu beams @ ISOLDE: p (1.4 GeV) +UCx + resonant laser ionization (RILIS).
 2005: Coulomb excitation of odd-odd 68,70Cu;
 2006: Coulomb excitation of odd-mass 67,69,71,73Cu.
N=50
g9/2
The odd-odd
68,70Cu
p3/2  g9/2 = 3-, 4- , 5- , 6-
g9/2
l
p1/2
f5/2
p3/2
28
40
llllll
llll
28
llllllll f7/2 llllllll


68Cu
39
g9/2
l
l
p1/2
f5/2
p3/2
28
l
40
ll
llllll
llll
28
llllllll f7/2 llllllll


70Cu
41
 level schemes dominated by multiplets originating from the coupling of the odd
proton with the odd neutron;
 B(E2) values within the states of the p3/2  g9/2 multiplet offers important
information about the p-n residual interaction across N=40.
1350
(4-)
956
(3-)
6-
E2
(5-)
68Cu:
778 0.7 ns <T1/2 <4 ns
722 T1/2=3.75 min
-
2+
84 T1/2=7.84 ns
0 T =31.1 s
1/2
1+
68Cu
Coulex with post-accelerated 6- isomeric beams !
506
(5-)
1+
(4-)
E2
p3/2p1/2
p3/2g9/2
68,70Cu
242 T1/2= 6.6 s
228
101
T = 33 s
0 T1/2= 45.5 s
36-
1/2
-
39
70Cu
41
J.D. Sherman et al. PLB67 (77) 257; T. Ishii, JAERI-Review, 2002-029, 25.
70Cu: J. Van Roosbroeck et al., PRL92(2004)112501, J. Van Roosbroeck et al., PRC69(2004)034313.
Isomeric 68,70Cu beams @ Isolde
 technique based on in-source laser spectroscopy
(Ü. Köster et al., NIM B, 160, 528(2000); L. Weissman et al., PRC65, 024315(2000)).
 set the laser frequency to select and maximize the production of the isomer of
interest.
668Cu
61+
722
0


70Cu
6- (g.s.)
31+
1+ (g.s.)
+ postacceleration by REX-ISOLDE
1+ 242
3- 101
60



Experimental set-up for Coulex @REX-ISOLDE
Miniball:
8 clusters, 3 X 6 fold segmented
• 4 quadrants
• 16 annular strips ()
• 24 sector strips ()
DSSD detector
(16o-53o)
REXISOLDE
68m,70gCu
(6-)
E~2.83 MeV/u
120Sn
~2
mg/cm2
PPAC
Beam
monitor
Beam dump
detector
Coulomb excitation of odd-odd 68,70Cu
- first use of postaccelerated isomeric beams  68,mCu (2.83 MeV/u) @ 120Sn (2.3 mg/cm2)
coulex
(5-)
4E2
(3-)
178 (M1)
6-
956
778
722
68Cu
693
 70Cu (2.83 MeV/u) @ 120Sn (2.3 mg/cm2)
(2+)
1+
(5-)
coulex
4E2
(3-)
6-
84
85
0
506
228
127 (M1)
101
0
70Cu
I. Stefanescu et al., PRL 98, 122701(2007).
Comparison with shell-model calculations
Shell-model calculations for the valence
space outside the 56Ni core (e=1.5e,
e=0.5e) .
g9/2
g9/2
l
p1/2
40
p1/2
ll
f5/2
f5/2 llllll
p3/2
f7/2
*B(E2;6-4-) in 72Cu from R. Grzywacz et al., PRL 81, 766 (1998).
68,70Cu:
l
28
llllllll
protons
p3/2
f7/2
llll
28
llllllll
neutrons
I. Stefanescu et al., PRL 98, 122701(2007).
 collectivity in 70Cu influenced by the stabilizing effect of 68Ni;
 the poor agreement between the experiment and theory for 68,72Cu points to the
importance of proton excitations across the Z=28 shell gap.
68Cu:
releasing the energy of the 6- isomer
5-
 triggered -emission of high K-isomers
extensively investigated by Coulomb
depopulation, irradiation with bremsstrahlung,
synchrotron radiation or X-rays
4(3-)
6-
722 3.75 min
 depopulation scheme based on K-mixing
178Hf:
180Ta:
2+
1+
0
Energy
32+
M1
C. Schlegel et al., PRC 50, 2198(1994),
D. Belic et al., PRC 65, 035801(2002).
31.1 s
 instantaneous depopulation of isomers in
odd-odd nuclei based on their multiplet
structure
54-
A.B. Hayes et al, PRL 89(2002)/PRL 96(2006);
E2
6-
1+
I(I+1)
 possible scheme for triggered energy
release in odd-odd nuclei
67,69,71,73Cu
ll
(f7/2)-1
7/2-
p1/2
f5/2
p3/2
2+ (A-1Ni)
7/2-
p1/2
f5/2
1/2-
g9/2
40
l
Eex (MeV)
2006: Coulomb excitation of
2
p3/2
28
1
5/2shell-model
p3/2
3/267Cu
38
0
69Cu
40
71Cu
42
g9/2
73Cu
44
75Cu
46
B. Zeidman et al., PRC 18, 2122(1978)/R. Grzywacz et al., PRL 81, 766 (1998) /S. Franchoo et al., PRL 81, 3100(1998).
 rapid decrease of the energy of the f5/2 orbital beyond N=40 (monopole migration)
 systematic study of the evolution of collectivity across N=40 by Coulomb excitation
Coulomb excitation spectra
 67Cu (2.99 MeV/u) @ 104Pd (2 mg/cm2)
p3/22+(66Ni)
5/21/2-
p1/2
f5/2
p3/2
7/2-
 71Cu (2.95 MeV/u) @ 104Pd (2 mg/cm2)
7/2-
(1/2-)
454
1/25/2-
p3/22+(70Ni)
(5/2-)
(1/2-)
7/2-
3/2-
(3/2-)
104Pd
104Pd
 69Cu (2.97 MeV/u) @ 104Pd (2 mg/cm2)
p3/22+(68Ni)
1/2-
 73Cu (2.88 MeV/u) @ 120Sn (1.7 mg/cm2)
7/25/21/2-
5/2-
3/2-
p3/22+(72Ni)
(1/2-)
135
5/2-
(7/2-)
(5/2-)
(1/2-)
(3/2-)
73Ga
7/2104Pd
(7/2-)
120Sn
7/2-
Experimental results (preliminary)
 rapid decrease of the energy of the 5/2- state
beyond N=40 followed by a decrease in
collectivity;
 rapid decrease of the energy of the ½- state
beyond N=40 followed by an increase in
collectivity.
low energy, high B(E2). Deformation?
R.L. Robinson et al., Phys. Rev. 134, B567, 1964.
Experimental results (preliminary)
B(E2; 7/2-  3/2-)  B(E2; 2+  0+) in
agreement with the proposed p3/2 2+ nature
for the 7/2- states;
 B(E2; 7/2-  3/2-) : minimum collectivity at
N=38;
 trend in the odd-Cu isotopes similar to that
shown by the even-even Zn isotopes.
Experimental results (preliminary)
B(E2; 7/2-  3/2-)  B(E2; 2+  0+) in
agreement with the proposed p3/2 2+ nature
for the 7/2- states;
 B(E2; 7/2-  3/2-) : minimum collectivity at
N=38;
 trend in the odd-Cu isotopes similar to that
shown by the even-even Zn isotopes.
strong polarization of the 66Ni
core by the p3/2 proton.
Summary and outlook
 2005: REX-ISOLDE postaccelerates first isomeric beams;
 postaccelerated isomeric beams to be used for transfer reactions, magnetic
moment measurements, etc;
 68Cu: first clear evidence for instantaneous depopulation of a nuclear isomer;
 measured B(E2; 6- 4-) indicate a fragile stabilizing effect of the Z=28 and N=40
gaps;
 2006: systematic study of the evolution of collectivity across N=40 by Coulomb
excitation with beams of 67,69,71,73Cu;
71,73Cu: coexistence of a deformed ½- state with a single-particle-like 5/2- level.
 Summer 2007: beamtime accepted for Coulex of
72,75Cu
@ REX-ISOLDE
 new experimental set-up for transfer reactions, HIE-ISOLDE (5-10 MeV/u)
Experimental results (1)
67Cu
5/21/27/2104Pd
69Cu
1/25/27/2-
DC for A=69
2340 (f )-1
7/2
7/2-
1670 p 2+ (66Ni)
3/2
1/2-
1170
5/2-
1115
3/2-
DC for A=67
104Pd
7/2-
67Cu
38
7/2-
1871 p 2+ (68Ni)
3/2
7/2-
-1
1711 (f7/2)
5/2-
1213
1/2-
1096
3/2-
69Cu
40
Experimental results (2)
(1/2-)
454 keV
71Cu
7/2104Pd
(7/2-)
1190
(7/2-)
981
(5/2-)
534
(1/2-)
454
p3/22+ (70Ni)
(f7/2)-1
71Ga
DC for A=71
71Cu
(1/2-)
5/2-
120Sn
DC for A=71
(3/2-)
71Cu
42
Experimental results (3)
(1/2-)
73Cu
5/2-
DC for A=73
Laser ON
(7/2-)
73Ga
120Sn
1010 (f )-1
7/2
(7/2-)
961
(5/2-)
166
(1/2-)
135
p3/22+ (72Ni)
7/2-
Laser OFF
(3/2-)
73Cu
44
j> = l+1/2
f5/2
f7/2
j< = l’-1/2
j> = l’+1/2
protons
neutrons
g9/2
Radioactive beams of
67,69,71,73Cu
@ISOLDE
1.4 GeV proton beam
UCx target
REX-ISOLDE
XCu+XGa
~2.95 MeV/u
Resonant laser
ionization (RILIS)
Miniball
68Cu
6- beam
68Cu
1+ beam