Shell and Shape effects investigated at (REX) ISOLDE
-
Upload
wendy-cash -
Category
Documents
-
view
43 -
download
0
description
Transcript of Shell and Shape effects investigated at (REX) ISOLDE
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Shell and Shape effects investigated
at (REX) ISOLDEElisa Rapisarda
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
126
82
50
50
28
20
828
The richness of Nuclear properties
82
N=Z
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
CERN ISOLDE Isotope Separator On-Line DEvice
ISOLDE:• delivers high-quality beams of a wide range of radioactive isotopes• unique position world-wide• post-acceleration of the existing ISOLDE beams with REX-ISOLDE up to 3 MeV/u
RILIS: Resonant Ionization Laser Ion Source
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
MINIBALL ISOLTRAP
GLM GHM
CRISCOLLAPSE
WITCH
WINDMILL
CERN ISOLDE Isotope Separator On-Line DEvice
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Down & Up Along the Nuclear Chart
82
50
126
82
50
28 Evolution of Shell structure• Coulomb Excitation Cu, Zn, … ;• Transfer reaction (d,p), (3He,p);• - decay of Mn, Fe, Co, Ni, …;• Laser spectroscopy Co, Ni, Cu, …;• Mass measurements
Shape-coexistence•Coulomb Excitation Hg, Po, Pb, Ra, Rn;• +/EC of Pb, Tl;•Laser spectroscopy Po, Pb, Tl;•-decay•Mass measurements
N=40
N=104
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
N=40 and Coulex of the Cu isotopes
high E(2+) in 68Ni (R. Broda et al., PRL 74 (95) 868) low B(E2, 0+ 2+) (Sorlin et al., PRL 88 (2002))
proposed new magic number N=40
n-rich Cu isotopes provide an excellent means for testing the proton-neutron residual interaction in this mass -region;
2003 Mass measurement ISOLTRAP and β-decay;
2005-2008: Coulomb excitation of odd-odd 68,70Cu;
2006: Coulomb excitation of odd-mass 67,69,71,73Cu.
N=4
0 N=5
0
Coulomb excitation of isomeric states of 70Cu
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
The odd – odd 70Cu
70Cu: J. Van Roosbroeck et al., PRL92(2004)112501, J. Van Roosbroeck et al., PRC69(2004)03431370Cu: J. D. Sherman et al., Phys.Lett. B67(1977)27568,70Cu: I. Stefanescu et al., Phys.Rev. Lett 98(2007)122701
0
228
242
T1/2= 33 s
506 (10)
T1/2= 6.6 s
6-
3-
4-
1+
(5-)
70Cu41-
T1/2= 45.5 s
101
E2
the low-energy level schemes dominated by multiplets originating from the coupling of the odd proton with the odd neutron p3/2 g9/2 = 3-, 4-, 5-, 6- or p3/2 p1/2 = 1+, 2+
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.
g9/2
f7/2
40
llllllll llllllll
llllllllll
l
p3/2
f5/2
p1/2
l
2828
70Cu41
ll
V. Paar Nucl.Phys.A331(1979)16
Coulomb excitation of isomeric states of 70Cu
Mass Measurement, -decay
Transfer reaction 70Zn(t,3He)70Cu
Coulomb Excitation
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Isomeric Beams from REX-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.
+ postacceleration by REX-ISOLDE
6- (g.s.)
1+
70Cu 3-
6-
1+
0
242
3-
101
J. V
an R
oosb
roec
k et
al.,
PRL
92(2
004)
1125
01
Coulomb excitation of isomeric states of 70Cu
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Experimental details6- (g.s.)
1+
70Cu 3-
6-
1+
0
242
3-
101
Isomeric Composition determined from characteristic beta decay lines
70Cu on 120Sn
Beam energy: 2,83 MeV/u
Beam Intensity: 5 X 105 pps
disentangle (6- XXX) and (3- XXX)
Inclusive excitation cross-sectionInclusive excitation cross-section
70Cu/70Ga = 80%/20%70Cu:
6- 86% 3- 7%1+ 7%
70Cu/70Ga = 50%/50%
70Cu:6- 72% 3- 25%1+ less than 3%
68,70Cu: I. Stefanescu et al., Phys.Rev. Lett 98(2007)122701
Coulomb excitation of isomeric states of 70Cu
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
70Ga contamination
The separator is not able to separate 70Cu from 70Ga
70Ga and 70Cu impinges both on target
Laser ON – Laser OFF to disentangle Cu interaction from Ga interactions
Laser ON 70Cu + 70Ga
Laser OFF 70Ga
Ga contribution can be precisely subtracted provided a precise normalization of Laser ON laser OFF run
Laser ON-OFF mode
Coulomb excitation of isomeric states of 70Cu
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Experimental Setup
70Cu 2,9 MeV/u on 120Sn 2,3 mg/cm2
REX-ISOLDE
Coulomb excitation of isomeric states of 70CuCoulomb excitation of isomeric states of 70Cu
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
127 keV
511 keV
Coulomb Excitation of 70,gsCu and 70,m1Cu
6-
3-
4-
5-
0101
228127 (M1)
E2
E2
511 (M1)
A=70DC
A=120DC
1171 keV
(506) 511
Coulomb excitation of isomeric states of 70Cu
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Cross Section: 127 KeV
DC for A=7070Cu (4- 3-)
127 keV
• CLX code• Matrix element = 0.23(3) eb•B(E2, 3- 4- ) = 73(10) e2 fm4
• CLX code• Matrix element 0.30(4) eb•B(E2, 6- 4- ) = 69(9) e2 fm4
Measurement of the (4- 3-) cross section in both experimentsIsomeric Composition of the 70Cu beam is known Disentangle the (6- 4-) and (3- 4-)
6-
70Cu
3-
4-
5-
0 T1/2= 44.5 s
101 T1/2 = 33 s
228
511
127 keV
Coulomb excitation of isomeric states of 70Cu
CEd
B(E2 : 0 2 )d
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Challenge to measure
Cross-Section 511 KeV
6-
70Cu
3-
4-
5-
0 T1/2= 44.5 s
101 T1/2 = 33 s
228
(506) 511 511 keV
???
DC for A=7070Cu (5- 6-)
511 keV
• CLX code• Matrix element 0.308(19) eb• B(E2, 3- 5- ) = 136(15) e2
fm4
Assuming only (3- 5-) excitations
Upper Limit
Coulomb excitation of isomeric states of 70Cu
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Z=28 N=28
• realistic interaction (M. Hjorth-Jensen et al. , Phys.Rep.26(2004)
• model space is 1f5/22p3/22p1/21g9/2 outside the 56Ni
inert core;
SMI Calculations by N. Smirnova
Shell Models: comparisonLarge Shell-Model calculations with ANTOINE code
• hybrid interaction (S.Lenzi et al., PRC82, 05430(2010)) + evolution of the proton gap from 68Ni to 78Ni;
• model space is 1f7/21f5/22p3/22p1/2 for protons and
1f5/22p3/22p1/21g9/22d5/2 for neutrons outside the 48Ca inert
core;
Coulomb excitation of isomeric states of 70Cu
SMII Calculations by K. Sieja
1g9/2
2p1/2
2p3/2
1f5/2
• NO proton-core excitations
• NO neutron-core excitations
Systematics of the 6- 4- transition
Z=20 N=28
2p1/2
2p3/2
1f5/2
1f7/2
2d5/2
Neutrons excitations across N=50
Proton excitations across Z=28
1g9/2
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
82
50
126
82
50
28
Shape-coexistence
Down & Up Along the Nuclear Chart
Shell structureN=40
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
A classical example: 186Pb
o Shape coexistence = proximity of spherical and/or deformed shapes(s) at low energy (E < few MeV)o 186Pb: most dramatic examples where the three lowest lying states are 0+ states of three different shapes within less than 700 keV.
A.N. Andreyev et al., Nature 405(2000)430
0+ 0+ 0+
Probe shape-coexistence in 182Hg via -decay of 182Tl
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Shape coexistence in Hg isotopes
Evidence for shape coexistence in systematic
energy levels: flat behaviour of the spherical
states against parabolic intrusion of the
deformed states with a minimum at mid-shell
N = 104.
slightly oblate ground state band
excited prolate band
Mid-shell N = 126
Probe shape-coexistence in 182Hg via -decay of 182Tl
2008: Coulomb excitation of even-even 182-184-186-188Hg;
2010-2011: -decay and laser spectroscopy of odd-odd 178-180-182-184-186Tl;
2010-2011: laser spectroscopy of odd-even 179-181-183-185-187Tl;
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Reorientation in Coulomb Excitation
0+
2+
The cross section for exciting the 2+ state DOES NOT only depend on its reduced transition probability B(E2: 0+ -> 2+), but also on the diagonal matrix element <2+||M(E2)||2+>.
CEd
B(E2 : 0 2 )d
Probe shape-coexistence in 182Hg via -decay of 182Tl
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
0+
2+
Obtain sensitivity on the diagonal matrix element of the first excited state by scanning the center of mass angular range!
Coulomb Excitation of 182,184, 186,188Hg
The detected γ yields of the photo peaks can be used to extract:• transitional matrix elements (B(E2) values)• diagonal matrix elements (quadrupole moments)
Program GOSIA: by fitting the matrix elements to produce the obtained γ yields by a χ2 minimization. (T. Czosnyka et al, GOSIA2)
Measurement of the nuclear shapes DIRECTLY
To help fit:• precise level scheme;• decay properties (E0 component);• lifetime measurements
Probe shape-coexistence in 182Hg via -decay of 182Tl
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Spectroscopy methods
in beam
182Tl 182Hg 186Pb 190Po
T. Grahn et al. PRC80(2009) 014324
h.s.l.s.
decay
0+
2+
4+
0+
N. Bree & A. PettsCoulex
2+
4+
6+
0+
0+
0+
J. Heese et al. PLB302(1993) 390
0+
decayA. Andreyev et al. Nature 405 (2000) 430
Transfer reactions
Ground State propertiesMass measurements (direct, decay)
Laser Spectroscopy
T. Cocolios et al. PRL106(2011) 052503H. De Witte et al. PRL98(2007) 112502
What are the observables (“Shape coexistence in atomic nucleus”, K.Heyde and J.Wood, Rev.Mod.Phys., in press)
E0 component
180Hg, J.Elsevier et al., PRC 84, (2011) 034307
Probe shape-coexistence in 182Hg via -decay of 182Tl
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
t1/2=2.6s
178Au182Hg
b+/EC a
gg
a
178Pt
b+/EC
182Au
4%
(15%) (85%)
t1/2=3.1s
t1/2=10.8s
t1/2=15.6st1/2=21.1s
182Tl
97.5%
-decay spectroscopy
182Tl101
= 101
1g7/2
2d5/2
1h11/2
2d3/2
3s1/2
1h9/2
2f7/2
1h9/2
1i13/2
3p3/2
2f5/2
2g9/2
3p1/2
= 81
50
82126
82
3s1/2 1i13/2 = 6+, 7+ or
3s1/2 1h9/2 = 4-, 5- or
3s1/2 3p3/2 = 1-, 2-
1h9/2 i13/2 = (2-, 11-)
ISOMERISM in 182Tl?
KEY FEATURES- Decay dominated by selection rule: l = 1,0-low-lying non-yrast coexisting states-E0 component of intraband transition
E0 component
?
[1] K.S. Bindra et al., Phys. Rev. C, 51 (1995) 401
Probe shape-coexistence in 182Hg via -decay of 182Tl
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
-spectroscopy: Experimental Setup
Windmill Chamber
Annular Si Si
pure 30 keV Tl beam from RILIS+ISOLDEIntensity = 104 pps
C-foils20 mg/cm2
Si detectors
SiAnnular Si
ff
ff
a
30 keV beam from ISOLDE
C-foil
Ge detector #1
Courtesy of Thomas E. Cocolios
Probe shape-coexistence in 182Hg via -decay of 182Tl
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
and Si- coincidences
g1 - g2 coincident:
or
g1
g1g2
g2Gamma coincidences with 8+ 6+ (413.2 keV)
E0 K-component 335KeV Si coincidences with 639 keV
g1 = 639 keV
E0
Probe shape-coexistence in 182Hg via -decay of 182Tl
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Result: infer ground state of 182Tl
s1/2 i13/2 = 6+, 7+ or s1/2 h9/2 = 4-, 5- or s1/2 p3/2 = 1-, 2-
*
**
*
**
**
*****
Probe shape-coexistence in 182Hg via -decay of 182Tl
[1] K.S. Bindra et al., Phys. Rev. C, 51 (1995) 401
f7/2
h9/2
i13/2
p3/2
f5/2
g9/2
p1/2
g7/2
d5/2
h11/2
d3/2
s1/2
h9/2
= 81
50
82
= 101
126
82
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
Result: , and level mixing +20 +
32+20 state: 335 keV
- identified by looking at Si-g coincidences- already placed at 328 (12) keV from -decay of
186Pb [1]
- g rays coincident with this Si energy: 639 keV
182Hg0+
0+2+
2+
4+
(2+)
8+
0
335351548612
973
1358
548
213
197
9446+
1124(4+)
E0
+22 +2 transition: 197 keV
- important E0 component (ICC = = 4.2 (8))
- the two levels are mixed;- the two levels have different deformation
CEII
Evidence for shape coexistence: transitions with E0 components are a model-independent signature of the mixing of configurations with different
mean-square radii
[1] J.Wauters et al., Phys. Rev. C, 50 (1994) 2768
+24 state: 1124 keV
- suggested in [2] but the 772.6 transition could not be seen
- from the energy systematics of the even-even Hg isotopes is a good candidate for 4+ member of the oblate
band[2] M. Scheck et al., Phys. Rev. C, 81 (2010) 014319
639
621.9 772.6
576.6
state: 973 keV- based on unambiguous coincidence relations- band-head of vibrational band on top of prolate
band- (621.9 keV): no E0
component
+32
+
32 +
22
Probe shape-coexistence in 182Hg via -decay of 182Tl
180Hg, J.Elsevier et al., PRC 84, (2011) 034307
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
82
50 126
82
50
28
N=40
Shape-coexistence
But new possibilities arise: ‐ multiple Coulomb Excitation ‐ transfer reactions ‐ spins, moments and radii measurements in previously hardly accessible regions
Although we have different experimental probes at our disposition, we still do not have a full picture of many phenomena
Down & Up Along the Nuclear Chart… a large world to explore
CERN, ISOLDE, 5th October Elisa Rapisarda, KULeuven
IKS Leuven, Belgium - I. Stefanescu, J. Diriken, N. Bree, M. Huyse, O. Ivanov, J. Van de Walle, P. Van Duppen
IPN Orsay, France - S. Franchoo
CSNSM Orsay, France - G. Georgiev, E. Fiori, R. Lozeva
IKP Köln, Germany A.Blashev, B.Bruyneel, J.Eberth, Ch.Fransen, K. Geibel, H.Hess, J.Jolie, M.Kalkuehler, P.Reiter, M.Seidlitz, N.Warr
TU München, Germany - Th. Kröll, R. Krücken, K. Wimmer
University of Camerino, Italy - D.L. Balabanski, K. Gladnishki, G. Lo Bianco, S. Nardelli
Warsaw University, Poland - J. Iwanicki, K. Hadynska, K. Wrzosek, M. Zielinska, J. Srebrny
University of Edimburg, Scotland – T. Davinson
Universiteit Ghent, Belgium - K. Heyde, N. Smirnova
CERN, Geneva, Switzerland - P. Delahaye, D. Fedorov, V. Fedosseev, U. Köster, B. A. Marsh, F. Wenander
and the ISOLDE and MINIBALL collaborations
Collaboration
Acknowledgement: Marie Curie Intra-European Fellowship of the EC’s FP7
IKS Leuven, Belgium - I. Darby, J. Dirichen, J. Elseviers, N. Bree, M. Huyse, D. Pauwels, D. Radulov, P. Van de Bergh, P. Van Duppen
University of West Scotland, UK – A.N. Andreyev, V. Liberati, Joe
Comenius University, Bratislava, Slovakia - M. Venhart, S. Antalic, M. Veselsky, Zdenka
University of Manchester, UK – I. Tsekhanovich
University of Ioannina, Greece – N. Patronis
Institute Laue Langevin, Grenoble, France - U. Köster
CERN, Geneva, Switzerland – T. E. Cocolios, V. Fedoseev, B. A. Marsh, M. Seliverstov, Anatoly, Pavel