NUCLEAR SPECTROSCOPY AT
THE DEPARTMENT OF NUCLEAR PHYSICS – TANDEM
BUCHAREST
NUPECC – Bucharest – Oct. 2007
• 1974 – 7 MV
• 2007 – 9 MV
• 3 ion sources:
- duoplasmatron (HVEC)
- sputtering (NEC)
- AMS ultraclean (sputtering)
• beams: p to Au (no noble
gases)
(~ 3600 hours/year)
Since 2006
Refurbishing process:
- Vacuum equipment √
- Electrical power supplies √
- Voltage charging system (Pelletron) √
- Sputtering ion source √
- Automatic control of ion optics &
diagnosis
- Beam pulsing system
• foil and gas stripping
• 7 beamlines
NUPECC – Bucharest – Oct. 2007
Experimental Nuclear Spectroscopy program
at the Bucharest Tandem accelerator
• Medium / high-spin γ-ray spectroscopy with
heavy-ion fusion-evaporation reactions
( check of structure models: shell model, IB(F)M )
• Low-spin γ-ray spectroscopy with p/α beams
(quasicomplete level schemes, DSAM lifetimes)
• Beta decay studies
( tests of critical point symmetries )
• Reactions of astrophysical interest [ (α,γ) ]
NUPECC – Bucharest – Oct. 2007
Heavy-ion fusion-evaporation reactions
NUPECC – Bucharest – Oct. 2007
139Ce
Low spins – quasicomplete low-spin scheme
139La(p,nγ) reaction , E = 5-6 MeV
p
High spins –
130Te(12C,3nγ),
50 MeV
D.Bucurescu et al, Eur. Phys. J. A27 (2006) 301
NUPECC – Bucharest – Oct. 2007
50
Sn
48
Cd
46
Pd
44
Ru
42
Mo
40
Zr
38
Sr
36
Kr
34
Se
32
Ge
30
Zn
28
Ni
R4/2
S4
2.18
-
(1.86)
2.22
(2.27)
1.9
2.16
(2.27)
2.07
2.27
2.23
(-1.78) (-0.59) -0.24 -0.37
2.33
2.36 (2.24)
2.29
-0.23 -1.45 (-0.74) (-1.09)
(2.81)
2.44
(-0.68)
2.15
-0.61
2.07
-0.73
2.02
(-1.63)
2.56
2.54
(-0.43)
2.46
(-0.72)
2.38
-0.24
2.46
(0.12)
-
40
42
(2.85)
-
-
-
(2.11)
-
(2.29)
-
(2.24)
-
(2.14)
-
(2.34)
-
2.34
-0.26
2.32
-0.35
2.33
-0.28
2.45
0.34
2.5
(0.08)
(1.92)
-
E 4   E 3   E 3   E 2 

E 2 

-
S








g
R4 / 2  2.2
2.23
2.11
2.02
2.22
(-0.42)
2.07
2.23
(-0.07)
2.34
2.38
(-0.37)
2.55
2.65
0.45
0.4
2.54 (2.64)
(0.3)
(2.16)
-
S  1.39
64
Zn,64Ge
E(5) Candidates
E(5): critical point of transition
28
30
32
34
36
38
44
46
48
50
U(5) (sph. vibr.) to O(6)(γ -soft)
N
(2.00, -1.0)
54
12C:
 /
(2.50,-2.0)
Fe( C, pn) Ga 
 Zn
12
64
36 MeV, 3 pnA, t=250 s,
54Fe:
64
13mg/cm2, 99%
3HPGe detectors ~30% eff.
C.Mihai et al, Phys. Rev. C75(2007)044302
NUPECC – Bucharest – Oct. 2007
64Zn
66Zn
B ( E 2;0 2  2 2 )
B ( E 2;0 2  21 )
1054
0.53
B( E 2;0 3  2 2 )
B( E 2;0 3  21 )
<0.66
210(75)
68Zn
-
E(5)
0 0.12
>430
0
32
NUPECC – Bucharest – Oct. 2007
-7
10
63
67
Cu() Ga
-8
Yield
10
-9
10
Cu(,)Ga, E = 6.3 MeV
2
present measurements
M.S. Basunia (PRC 75/2007)
GNASH-FKK (OM pot.: Avrigeanu)
NONSMOKER
5 foil (~ 1.0 mg/cm ) - stack
4000
Foil #4
E = 4.923 MeV
93
*
184
3000
-10
10
*
5
2000
10
300
10
67
Cu(,) Ga
Foil #2
E = 5.994 MeV
93
*
9
10
11
67
Cu() Ga
0
3000
8
E (MeV)
63
184
(,) (mb)
Counts
*
63
7
1
*
1000
6
0
-1
10
-2
10
*
2000
present
Basunia et al.
GNASH-FKK
NONSMOKER
-3
10
300
*
1000
-4
10
2
0
50
100
150
200
250
E (keV)
300
350
400
3
4
5
6
7
8
9
10
E (MeV)
NUPECC – Bucharest – Oct. 2007
Multi-purpose gamma-miniarray
3 new HPGe (pop-top)
(eff.: 2 x 60%; 1 x 30%)
+ 3 older ~30% + clover (to come)
+…
Under execution:
Plunger device (“Kőln”)
Under installation:
2007-2008: 6 Osiris
detectors with
anticompton shields
NUPECC – Bucharest – Oct. 2007
European Collaborations
• Collaborations with different Labs and Universities
(bilateral and governmental collaboration agreements)
Padova – Legnaro ; GANIL
•
EURONS (AGATA, EXOCHAP, ISIBHI, EWON)
• EURISOL (fission target; safety&radioprotection;
physics&instrumentation)
• FAIR (NUSTAR)
NUPECC – Bucharest – Oct. 2007
Collaboration with Lab. Naz. Legnaro
1) The heaviest even-even N=Z and odd-A N=Z+1
100Sn)
nuclei ( A > 80,
Fusion-evaporation reactions.
GASP (γ); ISIS (charged particles); N-ring (n)
NUPECC – Bucharest – Oct. 2007
NUPECC – Bucharest – Oct. 2007
• T=0 np pairing in N=Z nuclei (?)
• Evolution of collectivity (along N=Z line)
• Critical point symmetry (X(5) at N ≈ Z
≈ 38,40 ?)
• Spin-gap isomers (close to N=Z=50)
• Shell model description (test current resid. inter.)
NUPECC – Bucharest – Oct. 2007
Delayed Alignment in N=Z Nuclei
Signature of T=0 np pairing ?
J=0 T=1
J=1…2j T=0
N.Marginean et al, Phys. Rev. C63 (2001) 031303(R); C65(2002)051303(R)
NUPECC – Bucharest – Oct. 2007
2) Spectroscopy of neutron-rich nuclei
Multi-fragmentation reactions.
CLARA (γ); PRISMA (product nuclei)
•
58Cr:
yrast line – E(5) symmetry vs shell model
• Neutron-rich Fe nuclei (A = 61 to 66) – test of “fpg”
residual interaction in large-scale SM calculations
• Spherical n-rich
interaction
89Rb, 92,93Y
– test of “gwbxg” residual
NUPECC – Bucharest – Oct. 2007
89Rb
D.Bucurescu et al, Phys. Rev. C, in press
NUPECC – Bucharest – Oct. 2007
3) High-spin states of light nuclei (sd shell)
• Tests of large scale shell model calculations
(sdfp residual interaction)
• Isospin symmetry
> Large MED between ~pure sp
(f7/2) analog states;
> Different E1 decay pattern of
analog pos. parity states:
 importance of multipole
Coulomb & electromagnetic
spin-orbit terms.
F. Della Vedova et al, Eur. Phys. J. A27 (2006) 301
NUPECC – Bucharest – Oct. 2007
3) Nuclear moment measurements – ns-μs isomers
- g-factors - TDPAD method, Hext;
- electric quadrupole moments (Qs) – Electric Field Gradients
(noncubic crystalline lattices)
• High K isomers:
Iπ=14+ in 176W :
well defined K=14, deformed pure 4-qp state;
anomalous decay due to K mixing in lower K states.
• Qs for normal and intruder states in 192,194Pb (11-, 12+):
shape mixing
• Qs for magnetic rotational bandhead in 193Pb
NUPECC – Bucharest – Oct. 2007
Qs
29/2- magnetic rotational bandhead in 193Pb
EFG Hg crystalline lattice T=170 K
29/2E=213 keV
T1/2 = 9 ns
21/2-
33/2+
E=184 keV
E=532 keV
T1/2 = 22 ns
T1/2 = 180 ns
|Qs | (exp)
Qs(PQTAC)
β2
29/2
(1i13/21)   ( 1i13/2 1h9/2)
2.84 (26) eb
–2.8 eb
– 0.12
21/2
(1i13/22 )  3p1/2
0.22(2) eb
+0.26 eb
+0.02
33/2
(1i13/23)
0.45(4) eb
+0.46 eb
+0.03
M. Ionescu-Bujor et al., Phys. Rev. C 70, 034305 (2004)
and to be published
NUPECC – Bucharest – Oct. 2007
Contributions to Nuclear Structures Studies at GANIL
 Search for new nuclei and new decay modes
On proton-rich side:
 Discovery of Doubly Magic 48Ni
 Two-Proton Radioactivity of 45Fe
 First Observation of 55, 56Zn
 First observation of 54Zn and its decay by two-proton
emission
On neutron-rich side:
 Evidence for 34Ne, 37Na in a search for 40Mg (not observed)
deduced particle instability of 33Ne, 36Na
NUPECC – Bucharest – Oct. 2007
 Focal plane γ-spectroscopy: β-decay and new isomers
 β-delayed γ-n spectroscopy (with TONNERRE
coupled to clover detectors) of very neutron
rich nuclei around N=20 and N=28:
 β-decay of 32,33Mg and level scheme of 32,33Al.
 limits of the island of inversion
located around N=20 are not well defined.
 neutron-rich nuclei around N=28: new
lifetimes for 12 nuclei, new Pn probabilities,
new transitions in 45,46Ar.
TONNERRE multidetector, built jointly
by IFIN-HH and LPC-Caen; used in
GANIL and ISOLDE/CERN
 New Island of μs Isomers in Neutron-Rich
Nuclei Around Z = 28 and N = 40: study of 71Co,
73Co, 76Ni, 67Fe, 72Ni
 New Shape Isomer in the Self-Conjugate Nucleus 72Kr
(0+ isomer measured with combined γ – CE spectroscopy)
 Observation of 0+ isomer in 44S (shape coexistence)
NUPECC – Bucharest – Oct. 2007
Combined CE- spectroscopy of isomers populated in fragmentation
Sarazin et al.,
PRL 84(2000)5062
Nummela et al.,
PRC 63(2001)044316
Grevy et al., EPJA (ENAM 04)
=2.3±0.3 μs
44S
0+ isomer observed in 44S, and known isomer in
43S -- interpreted as shape coexistence
evidence in neutron rich N=28 nuclei
NUPECC – Bucharest – Oct. 2007
 In-beam γ– ray spectroscopy
Fragmentation reactions (double fragmentation) to populate
excited states in extremely far from stability nuclei.
( SPEG spectrometer and Chateau de Cristal)
 Search for neutron excitations across the N = 20 shell gap
in 25-29Ne
 N = 14 and 16 shell gaps in neutron-rich oxygen isotopes
 Structure of the neutron-rich 37, 39P and 43, 45Cl nuclei
 Shape evolution in heavy sulfur isotopes and erosion of the
N=28 shell closure

 Recent experiment for 42Si and 36Ca (collapse of N=28 magicity)
NUPECC – Bucharest – Oct. 2007
Collapse of N=28 Shell Closure in 42Si
B. Bastin et al., PRL99(2007)022503
DE
44S
secondary
beam
40Si
42Si
M/Q
New experimental
results and shell
model calculations
indicate that 42Si is
best described by a
well deformed oblate
rotor
E (2+) MeV
Chateau de Cristal -detector
Identification after 2nd
fragmentation using
SPEG spectrometer
NUPECC – Bucharest – Oct. 2007
Research group:
senior researchers: 8
researchers: 5
PhD students: 6
NUPECC – Bucharest – Oct. 2007
NUPECC – Bucharest – Oct. 2007
NUPECC – Bucharest – Oct. 2007
NUPECC – Bucharest – Oct. 2007
NUPECC – Bucharest – Oct. 2007
NUPECC – Bucharest – Oct. 2007
NUPECC – Bucharest – Oct. 2007
188Pb
triple shape coexistence
G.D.Dracoulis et al., Phys.Rev. C 67, 051301(R) (2003)
12 spherical
 (1i13/2)2
11– oblate
 (1i13/2 1h9/2)
8– prolate
 (1i13/2 1h9/21)
Static moment experiments - in progress at LNL
NUPECC – Bucharest – Oct. 2007
 Focal plane γ– spectroscopy. β-decay and New Isomers

New Island of μs Isomers in Neutron-Rich Nuclei Around
the Z = 28 and N = 40 Shell Closures
 Beta-decay of 71Co and 73Co
 Evidence for an isomer in 76Ni
 Isomeric decay of 67Fe -- Evidence for deformation
 Low energy levels in 72Ni
 New Shape Isomer in the Self-Conjugate Nucleus 72Kr
(0+ isomer measured with combined – CE spectroscopy)
 Observation of 0+ isomer in 44S (shape coexistence)
NUPECC – Bucharest – Oct. 2007
-delayed n- spectroscopy with TONNERRE
32Mg
decay
TONNERRE installed in focal plane of
LISE-III Spectrometer
TONNERRE was built joint by IFIN-HH and LPC-Caen.
It has ~ 50% angular coverage and 25% typical intrinsic
resolution for few MeV neutrons. The threshold
corresponds to about 300 keV neutron energy.
TONNERRE was used in GANIL and ISOLDE/CERN.
Typical implantation setup allows
measurements
of --n
coincidences.
NUPECC
– Bucharest
– Oct. 2007
> Large MED between ~pure sp
(f7/2) analog states;
> Different E1 decay pattern of
analog pos. parity states:
 importance of multipole
Coulomb & electromagnetic
spin-orbit terms.
F. Della Vedova et al, Eur. Phys. J. A27 (2006) 301
NUPECC – Bucharest – Oct. 2007
4) Nuclear moment measurements  isomers ns - µs
Dedicated experiments
Hyperfine interactions  TDPAD method
g factors Hext
Qs
Vzz Electric Field Gradients
• Home
new isomers, g, Qs
• INFN LNL
g, Qs
noncubic crystalline lattices
→ nuclei near stability
→ neutron deficient nuclei
A180 K isomers , shape coexistence in Pb
• GSI RISING collaboration
g → neutron rich nuclei
NUPECC – Bucharest – Oct. 2007
g Qs
176W
Anomalous
decay
f
917 keV
714 keV
945 keV
I= 14+
high K isomer
High K states
E transitions
 = ΔK –  degree of K forbiddenness
f= (T1/2 /T1/2W) 1/
2.3
3.0
3.6
fν  100 normal decay
LNL
164Dy(16O,4n)176W
Pulsed beam
83 MeV
DT=2 ns Trep=800 ns
T1/2=41(1) ns
B. Crowell et al., PRL 72, 1164 (1994)
NUPECC – Bucharest – Oct. 2007
176W
I =14+
g factor Hext = 27.5 kG
Qs EFG Tl crystalline lattice
gexp = + 0.462 (11)
 7/2+ [404] 9/2- [514]  5/2- [512] 7/2+ [633]
|Qs | = 6.0 (7) eb
• deformed pure four – quasiparticle configuration
2 (14+) =
•
well defined K = 14
0.29(4)
•
anomalous decay
due to K mixing in the lower K states
M. Ionescu-Bujor et al., Phys. Lett. B 495, 289 (2000)
Phys. Lett. B 541, 219 (2002)
NUPECC – Bucharest – Oct. 2007
Qs normal and intruder states in 192,194Pb
EFG Bi crystalline lattice
12+ → 0.32 (4) eb
T1/2= 1080 ns
11- →
2.9 (3) eb
T1/2 = 758 ns
 (1i13/2 )2
11
 1i13/21h9/2
12+ 2  + 0.02
0.48 (3) eb
T1/2 = 370 ns
12
---- PQ
---- PQ TAC
11
2  –0.12
3.6(4) eb
T1/2 = 133 ns
IBM
HFB
Qo (11, 192Pb)  shape mixing
M. Ionescu-Bujor et al., Phys. Lett. B 650, 141 (2007)
NUPECC – Bucharest – Oct. 2007