Slides - Agenda

Study of shell structure and order-to-chaos
transition in warm rotating nuclei with the
radioactive beams of SPES
G.Benzoni, S.Leoni, A.Bracco, N.Blasi, F.Camera, F.C.L.Crespi, B.Million,O. Wieland,
P.F. Bortignon, G. Colò, E. Vigezzi
Università degli Studi and INFN sez. Milano
D. Bazzacco, S. Lenzi, S.Lunardi, D.Montanari, et al.
INFN Padova and Università degli Studi di Padova
G. DeAngelis, D. Napoli, J.J. Valiente-Dobon, et al.
Laboratori Nazionali di Legnaro INFN
A. Maj, P. Bednarczyk, B. Fornal, M. Kmiecik, M. Ciemala et al.,
The Niewodniczanski Institute of Nuclear Physics, Polish Academy of
Sciences, Krakow, Poland
Warm rotating nuclei
Collective rotations: de-excitation spectra
168Yb
Analysis of quasi-continuum g-g
coincidence spectra with
statistical and spectral shape
analysis methods
1200
Eg2
Npath 
Fluctuation Analysis Method
Neve
 P2
μ2
-1
μ1
42/
42/
600
600
Eg
1200
Main Results from the Analysis of
Quasi-Continuum Rotational Spectra
Evidence for rotational damping
 Sensitivity to the residual interaction
 Collectivity with thermal energy
 Mass dependence
 Configuration dependence
 Measurement of Compound and Rotational Damping Width
 Superdeformation at finite temperature
i) how large the damping width Grot is and how it changes with
excitation energy and spin;
ii) at which energy rotational damping sets in and how gradual is the
process;
iii) whether or not this process depends on the intrinsic nuclear
configuration, therefore leading to different effects in connection
with different quantum numbers of the shell-model states, such as the
K-quantum number;
iv) how high in excitation energy one has to go before a fully chaotic
regime is reached.
A. Bracco and S. Leoni, Rep. Prog. Phys. 65(2002)299
Configuration Dependence & Onset of Chaos
Persistence of selection Rules with Temperature:
Chaotic regime:
U  2.5 MeV
Smaller number of
High-K states in the
damping regime
Low K
High K
10
Need for confirmation in other systems: egs. Hf nuclei
136Te+48Ca
 180Hf +4n
G. Benzoni et al.,PLB615 160-166 (2005)
Warm rotation in exotic systems
Stable:48Ca(@ 215MeV)+124Sn168Yb(63)+4n
SPES: 132Sn(@ 560MeV)+48Ca
176Yb(76)+4n
Spin and temperature dependince of Grot
Stable:48Ca(@ 215MeV)+124Sn168Yb(63)+4n
SPES: 132Sn(@ 560MeV)+48Ca
8
132Sn+48Ca
4
g-flow
E1/E2
2
0
10
20
30
40
Spin [h]
50
60
70
I+2
I
I-2
168
300
Grot [keV]
<U> [MeV]
Grot
48Ca+124Sn
6
0
176Yb(76)+4n
Yb
200
60
100
I=30
0
0
1
2
3
U [MeV]
4
40
70
50
5
6
Rotational Damping: I and T dependence
Grot and G from g-g spectra
a
E2 strength
400
163Er
350
fine structure
I-2I-2 of rotational damping
Counts [a.u.]
Width [keV]
Grot
I
G
I = 40, 41 h
200
22GG
150

100
0
20
30
40
50
60
Gnar
Gwide
2Grot
50 
Gwide
-100
discrete
U < 1 MeV
Spin [h]
Gnarrow  2G
100
-200
GG
rot
rot
<U> = 1.4 MeV
250
50
levels 11-100
0
<U> = 2 MeV
300
Dw0
150
– EUROBALL Data
0
100
(Eg1-Eg2) [keV]
200
S. Leoni et al., PRL93(2004)022501
F. Stephens et al., PRL88(2002)142501
M. Matsuo et al., PLB465(1999)1
70
Shell effects dependence
N(2)path
40 RIDGE ANALYSIS
30
168
164
Yb
114
Te
theory
Yb
20
114
10
Te
VALLEY ANALYSIS
N(2)path
104
103
10
164
Yb
114
2
101
Te
theory
1000
Eg (keV)
Grot a I A-5/2 e -1
U0
a A-2/3
comparative
study
0
105
So far MASS dependence
has been addressed
1500
A=110
114Te
e ≈0.25
I=40h,U=2MeV
highly aligned
orbits
106
A=160
164Yb
e ≈0.25
Grot depends on 2 contributions:
P and N . Accessing nuclei on an
isotopic chain wll help define the 2
contributions
for U ≤ 2 MeV
Grot  2(2Dw0)
168Yb
Dw0  (Dw0N)2 + (Dw0P)2
98
no highly aligned
orbits
neutron
Rotational Damping: I and T dependence
Proposed reactions
Experimental array
Need for a 4p g array:
Ge Ball (AGATA/GALILEO) + LaBr3 scintillators
Conclusions
Realistic Simulation of g-decay flow: E1/E2 competition
H ( I )  H def - wJ x + V
J z2
2rot
8
E1
Grot
E* (
2

2
n b   Sif 
 f

Bn
E2
MeV )
SDI
residual
15
p
n
extrapolated
r and Grot
Grot
Band-mixing Calculations
=> decay flow simulation
microscopic
discrete
levels
-1
onset
of
damping
nb = 2
168Yb
e = 0.25
I = 20-61 
400 levels
U  2.5 MeV
I+2
I-2 I
0
20
I (h)
yrast
60
A. Bracco et al. PRL76(1996) 4484