Isomer Studies
with RI-beam Induced Fusion Reactions
and In-Flight Fission Reactions

A. Odahara
Department of Physics, Osaka University

Isomer :one of good probes to obtain information
for change of nuclear structure
ex. shape isomer :caused by the sudden shape change
We apply isomer spectroscopy to study shape evolution.

spherical shape
single-particle mode

deformed shapecollective mode

as function of spin and isospin
How does nuclear shape change
by increasing angular momentum
and/orby increasing neutron or proton number?

High-spin shape isomers
in N=83 isotones
odd152Er : [ν(f47/2h9/2i13/2)π(h11/2 )]61/2+

151Ho: [ν(f37/2h9/2i13/2)π(h11/2 )]28-[ν(f7/2h9/2i13/2)πh11/22]49/2+

420ns(61/2+, 65/2-)
10.288

Excitation Energy [ MeV ]odd-odd [ν(f7/2h9/2i13/2)π(h11/22d5/2)]27+

oblateoblateβ ~ - 0.19
0.5s
27/2-2.586

10ns
13/2+ 1.140

spherical
23.5s
07/2151
68 Er

Results by the systematic studyof high-spin shape isomers in N=83 isotones
1. shape isomerwith high-spin

2. change ofthe Z=64 sub-shellgap energy
641h11/2
2d5/2

A. Odahara et al., Nucl. Phys. A620 ( 1997) 363

odd-even mass difference
3. experimental
B(Z) : binding energy
pairing interaction
E(Z) : excitation energy
in high-spin statesof the HSIπZ∆( Z ) =[{B( Z − 1) + E ( Z − 1)}2+ {B( Z + 1) + E ( Z + 1)} − 2{B( Z ) + E ( Z )}]A. Odahara et al., Phys. Rev. C 72 ( 2005) 061303

2.0∆(z) [ MeV ]A. Odahara et al.,J. Phys. Soc. Jpn 77 ( 2008) 114201

deformed independent particle model (DIPM)
by H. Sagawa

1.5ground state

1.00.50.0

HSI61 62 63 64 65

except for SD spins
Nuclear Chart :Experimental maximum spins which are mostly
not confirmed
reported in NNDC (-2008)

proton number

45≦Z≦8245≦N≦130

We developed
γ-ray spectroscopy method
using low-energy RI beam
( around 5 - 10 MeV/u )fusion reaction
at RCNP, Osaka University.
to search for isomers
in neutron-rich nuclei

82

50
2820828
8 20

to search for
high-spin shape isomers

126
82
50

neutron number

in-flight fission reaction- EURICA campaign –at RIBF, RIKENIsomer Studies
with RI-beam Induced Fusion Reactions
and In-Flight Fission Reactions

1. Isomer study in high-spin region
using RI-beam Induced Fusion Reaction
at RCNP, Osaka University
2. Isomer study in neutron-rich isotopes
using In-Flight Fission Reactions- experiment in EURICA campaign –at RIBF, RIKEN

1. Isomer study in high-spin region
using RI-beam Induced Fusion Reaction
at RCNP, Osaka University
OsakaTokyo

east experimental hall
EN beam line
(secondary beam line)

ring cyclotron
AVF cyclotronEN beam line
RCNP secondary beam line
F１Q3Q2F0D1SX1SX2Q4D2Q1Q5Q6Q7SX3F２T. Shimoda et al., NIM B70 (1992) 320.
S. Mitsuoka et al., NIM A372 (1996) 489.

RI beam with beam energy
from low (~ MeV/u)
to high (~several tens MeV/u )can be delivered.

Maximum rigidity
3.2 TmEnergy acceptance ∆E/E = 16 %Angular acceptance ∆θ = 40 mrad
∆φ = 28 mrad
Path length
16.8 mStudy of high-spin states of nuclei in transitional mass region
with Z~57 and A~130
primary reaction: 9Be(18O,17N)10B
9.3 MeV/u, 1.5 pµA
secondary reaction : 124Sn +17N  135La (6n), 136La (5n)5.5 MeV/u, 1.2x105 pps, around 60%
Ge detector array
12 tapered Ge+ 8 BGOACS(co-axial Ge det.
used in EUROBALL)
from gamma poolSi-ball
170 µm ∆E typeby Kyushu Univ.
& CNS, U. of Tokyo

total efficiency :around 3 %at 1.3 MeV
collaboration withFrench group( IPN, CNSMS, Orsay& Universite Paris Sud XI)

new isomer in 136La

time difference
between PPAC and Geprompt

delayednew isomer in 136La

T1/2=187(27) ns

by H. Nishibata

Clover Array Gamma-ray spectrometer
RCNP
future plan at RCNP/RIBF for Advanced research( CAGRA )# 10 clovers + Compton suppression shields
from CloverShare in USA# 6 clovers + Compton suppression shields
from Tohuku University.
N. Aoi (RCNP), E. Ideguchi (RCNP), A. Tamii (RCNP),
M.P. Carpenter (ANL), V. Werner (Yale),P. Fallon(LBNL), T. Koike (Tohoku)

Grand Raiden & LAS(double arm spectrometer)

EN beam line
(secondary beam line)

Search for high-spin states in transitional nuclei
with Z~57 and A~130
Dep. of Phys., Osaka Univ.
Univ. of Paris Sud, France
CNS, Univ. of Tokyo
RCNP, Osaka Univ.
RIKEN
Tokyo Univ. of Sci.
IPN Orsay, France
IPN Lyon, France
CSNSM Orsay, France
IPHC Strasbourg, France

H. Nishibata, A. Odahara, T. Shimoda,
Y. Ito, K. Tajiri, J. Takatsu
R. Leguillon, C. Petrache (CSNSM Orsay)
R. Yokoyama
E. Ideguchi, N. Hamatani, T. Suzuki
H. Watanabe, Y. Wakabayashi,
S. Nishimura, Y. Gono
K. Yoshinaga
D. Beaumel
G. Lehaut, D. Guinet
P. Desesquelles
D. CurienIsomer Studies
with RI-beam Induced Fusion Reactions
and In-Flight Fission Reactions

1. Isomer study in high-spin region
using RI-beam Induced Fusion Reaction
at RCNP, Osaka University
2. Isomer study in neutron-rich isotopes
using In-Flight Fission Reactions- experiment in EURICA campaign –at RIBF, RIKENEURICA (EUroball-RIKEN Cluster Array) project
decay spectroscopy : β-decay and isomer decay of nuclei far from stability line
using BigRIPS and Zero-degree separators

at RIKEN, RIBF

proton number* Shell-structure evolution around doubly- magic nuclei82
around 78Ni, 100Sn, 132Sn* Shape evolution from spherical to deformed shape* Proton 50drip-line nuclei
isospin symmetry,np paring etc.
28
20882

* Nuclear astrophysics
5082028

neutron number126

Survey of Decay Properties with EURICA
Half-lives (T1/2)

S. Nishimura

Isomer (T1/2)
A.Odahara (Z~55)

Beta-delayed gamma
Beta-delayed n, p
EC, Qβ, New isotopes

H.Watanabe (Z~46)

R.Gernhäuser (Z~50)

E.Ideguchi (A046)
R.Yokoyama (A047)
W.Jin(A069)

K.Moschner (A028)
A.Yagi (A043)
L.Sinclair (A042)

A.Jungclaus
G.Lorusso (A065)
Y.Shimizu (C006)
P.-A.Söderström (A035)

M.Niikura (Z~28)
G.Benzoni (Z~28)

Z.Y.Xu (A043)

T.Sumikama (A033)
F.Browne (A034)
I.Nishizuka (A066)

EURICA( Euroball-RIKEN Cluster Array )12 EUROBALL
Cluster Ge detectors
for γ ray

Detectors used in EURICA project
WAS3ABi( Wide-range Active Silicon Strip Stopper
Array for Beta and Ion detection )5 DSSSDs (Double Sided Silicon Strip Detector)
for RI beam and β rayBeam

40x60x1 mm(40x60 strips)

18 LaBr3 detectors
φ1.5 x 2”

for short life timemeasurement

plastic scintillator
for β rayas time referenceNP1112-RIBF87
Shape evolution in neutron-rich A~140 nuclei
beyond the doubly-magic nucleus 132Sn
Spokespersons :Atsuko Odahara
Radomira Lozeva
Changbum Moon
doubly-magic nucleus
132Sn (Z=50, N=82)

Osaka Univ. , Japan
IPHC, Strasbourg, France
Hoseo Univ., Korea

EURICA U beam campaign :β-γ spectroscopy
isomer spectroscopy

TeBa
Xeexperiment :30 April – 5 May, 2013(Live time : 3.5 days )Z > 50
N > 82neutron number

Systematic study ofshape evolution
from spherical to prolate shape
as increase of neutron number
Octupole correlations
is expected in this mass region.
well known in 146Ba (Z=56, N=90)

Search for isomers in n-rich Cs isotopes
55Cs

Z

54Xe
53I

52Te
51Sb

A/Q
Systematics
of known isomers
in Cs isotopes

ref : NNDC

by Osaka group
A. YagiSearch for isomers in n-rich Cs isotopes
We can search isomers with T1/2 > hundreds ns.
flight time [ F0 target – WAS3ABi ] : around 650 ns

time information to search for isomerstart :
beam at F11

stop :
γ-ray
by EURICA

Results : new isomers in n-rich Cs isotopes

by A. Yagi
145Cs (N=90)

147Cs (N=92)

T1/2 = 0.5 1 [µs]T1/2 = 0.19 2 [µs]148Cs (N=93)

146Cs (N=91)

T1/2 = 1.25 5 [µs]T1/2 = 4.8 2 [µs]Discussion : isomers in n-rich Cs isotopes(1) isomers in odd-odd Cs(2) isomers in odd Cs

new isomers

new isomers

low-energy transition
directly emitted
from the isomers

K isomer ?

K isomer[404]9/2- ?
Woods-Saxoncalculation codeby M. Yamagami

from the Exof isomers
β2 > 0.2 ?

Discussion : new isomers in n-rich Cs isotopes
Spins and parities of the ground states
Z N 82

84868890
92
Cs 55 7/2+ 7/2+ 7/2+ 3/2+ 3/2+ (3/2+)
NNDC

spin-parity 3/2+ of ground statein Cs isotopes with N=88, 90, 92
It is difficult to explain it
simply by single-particle level.
Z=55
N=88,90,92

G.A. Leander et al.,Phys. Lett. B 152 ( 1985 ) 284

octupole collectivity ?

A. Odahara1, R. Lozeva2, C.-B. Moon3, A. Yagi1, R. Daido1, Y. Fang1, H. Nishibata1,S. Nishimura4, P. Doornenbal4, G. Lorusso4, P.-A. Soderstrom4, T. Sumikama5,H. Watanabe6, T. Isobe4, H. Baba4, H. Sakurai7,4, F. Browne8,4, Z. Patel9,4,S. Rice9,4, L. Sinclair10,4, J. Wu11,4, Z.Y. Xu7, R. Yokoyama12, T. Kubo4, N. Inabe4,
H. Suzuki4, N. Fukuda4, D. Kameda4, H. Takeda4, D.S. Ahn4, D. Murai13,
F.L. Bello Garrote14, J.M. Daugas15, F. Didierjean2, E. Ideguchi16, T. Ishigaki1,H.S. Jung17, T. Komatsubara18, Y.K. Kwon18, C.S. Lee19, S. Morimoto1, M. Niikura7,4,I. Nishizuka5, T. Shimoda1, K. Tshoo18, P. Lee19
1 Department of Physics, Osaka University
2 IPHC/CNRS and University of Strasbourg
3 Hoseo University, 4 RIKEN Nishina Center
5 Department of Physics, Tohoku University
6 Beihang University
7 Department of Physics, University of Tokyo
8 University of Brighton, 9 Surry University
10 University of York, 11 Peking University
12 CNS, University of Tokyo
13 Rikkyo University, 14 University of Oslo
15 CEA/DAM, 16 RCNP, Osaka University
17 University of Notre Dame, 18 IBS
19 Chung-Ang UniversitySummary
1. Isomer study was performed to reveal shape evolution
as a function of spin and isospin.
2. Isomer study was carried out in high-spin region
using RI-beam induced fusion reaction
at RCNP, Osaka University.
(1) We developed γ-ray spectroscopy method
using low-energy RI beam (around 5-10 MeV/u)fusion reaction .
(2) We found the exotic isomer in 136La which locatestransitional and triaxial deformed region.
3. Isomer study was carried out in neutron-rich isotopes
using in-flight fission reactions
as one of experiments in EURICA campaign at RIBF, RIKEN.
(1) We found 4 new isomer in n-rich Cs isotopes.
(2) New isomers in odd-Cs supposed be candidate of K isomer.