Heavy-Ion Double Charge Exchange study !
via 12C(18O,18Ne)12Be reaction
Motonobu Takaki!
(CNS, The University of Tokyo)!

!

H. Matsubara2, T. Uesaka3, N. Aoi4, M. Dozono1, T. Hashimoto4, T. Kawabata5,
S. Kawase1, K. Kisamori1, Y. Kubota1, C.S. Lee1, J. Lee3, Y. Maeda6, S. Michimasa1,K. Miki4, S. Ota1, M. Sasano3, T. Suzuki4, K. Takahisa4, T.L. Tang1, A. Tamii4,H. Tokieda1, K. Yako1, R. Yokoyama1, J. Zenihiro3, and S. Shimoura1!
1!

CNS, The University of Tokyo!
2
National Institute of Radiological Science (NIRS)!
3
RIKEN Nishina Center!
4
Research Center for Nuclear Physics, Osaka University!
5
Department of Physics, Kyoto University!
6
Department of Applied Physics, University of Miyazaki

2nd conference on ARIS 2014, June 2nd 2014

Double Charge eXchange (DCX) reaction
Probe for unstable nuclei!
• Using stable target with ΔTz = 2!

Powerful tool to investigate
IV Double Giant Resonances!
• DIAS, DIVDR…

12C(π-,π+)12Be

J.E. Ungar et al., PLB, 144 333 (1984)
S. Mordechai et al., PRL 60, 408 (1988).

2

HIDCX with Missing mass method !
at Intermediate energy
Heavy-ion!
12C(14C,14O)12Be!

• Double Spin and/or Isospin flip (ΔS=2, ΔTz=2)!
CountsMissing mass method!

Sn

Elab=24A MeV• measure All excitation energy region
on a same footing!
25

Intermediate energy (~ 100MeV/u)!

- simple reaction mechanism!
• ΔL sensitivity of angular distributions!
- multipole assignment

We performed 12C(18O,18Ne) reaction experiment!
in normal kinematics at 80 MeV/nucleon.

151050 Ex

W. ! Oertzen et al.,"
NPA, 588 129c (1995)

d2σ/dΩc.m.dE (nb/sr/(0.5 MeV))• direct reaction process dominance!

2030

24Mg(18O,18Ne)24Ne !

at 76A MeV

20100

1
J. Blomgren et al.!
PLB, 362 34 (1995)

0051015

20

24Ne excitation energy (MeV)

3(18O,18Ne) reaction
Ground states of 18O and 18Ne are among
the same super-multiplet.!
• simple transition process!
• large transition probability!

!
B(GT) ~ 0.07!
!
!

B(GT)=0.11

τ

τ
18O

στ
B(GT)=3.15

18FστB(GT)=1.05

B(GT) ~ 018Ne

A primary 18O beam is employed!
• high intensity (> 10 pnA)!

Experiment can be performed at RCNP with GR spectrometer !
• high quality data with high energy resolution
4Setup of the experiment
Good PID resolution

Energy resolution = 1.2 MeV(FWHM)

1818Ne

1400

F

17F

ΔE in PL Scint.

17OE (arb. unit)

1200

1000

Grand Raiden

O

1618Ne
15O

14O

15N

14N

13N

13800

C

12C

1112C target (2.2 mg/cm2)

12N

600

C
11B

A/Q
1.7 1.8 1.9 2.0
2.1 2.2 A/Q
1.7

18O beam

MWDCs and plastic scinti.

beam: 18O
Energy: 80A MeV
ΔE: ~ 1 MeV
intensity: 25 pnA

1.8

1.9

2

2.1

2.2

2.3

18Ne

Ring Cyclotron Facility, !
Research Center for Nuclear Physics, !
Osaka University5

Successful result!
!
!

2+/3-!
!
!
!
!

Bound and unbound states were observedin one-shot measurement.!
The 2.2 MeV peak has a larger cross section than the g.s.!
Different angular distribution of the 4.5 MeV peak.

6

Probing of the configuration mixing
Mixing degree between p- and sd-shell components
in 0+ states of 12Be!
!
sd!

} mixing

1p1/2!

1p3/2!
(p)2 dominance!
!

1s1/2
proton12Be

neutron!

The cross section for the two 0+ states at forward angle!
➡dominated by double Gamow-Teller transition(ΔL=0, ΔS=2, ΔT=2).!
➡mainly reflect the p-shell contribution.
7

Evaluation of p-shell contribution to 0+ states of 12Be
Assumption:!
1. 12C g.s. has only p-shell configuration. !
2. The transition occurs in the 0hω

relative cross section between 0+g.s. and 0+2!
←→ ratio of p-shell contributions+(02 )/+(0g.s. ) = 2.4(2)only statistical error

Similar spectroscopic value with earlier worksp-shell contribution in 00+0+0methods
12Meharchant2560

2.4±0.5

Fortune3268

2.1

SMBarker

31421.4

SM

R. Meharchant et al., PRL 122501, 108 (2012)
H. T. Fortune et al., PRC, 024301, 74 (2006)
F. C. Barker, Journal of Physics G, 2(4), L45 (1976)8

Conclusion!
!
!

2+/3-!
!
!
!
!
!

The 2.2 MeV peak has a larger cross section than the g.s.!
• The p1/2 component dominantly contributes to the 0+2 state.!

The different angular distribution of the 4.5 MeV peak!
• The HIDCX reaction can assign multipolarities.
9

Summary
HIDCX reactions are unique probe for light unstable nuclei andIV double giant resonances, especially spin-flip excitations. !
The HIDCX 12C(18O,18Ne) reaction experiment was performed.!
• Three clear peaks were observed at Ex=0.0, 2.2 and 4.5 MeV.!
• Larger cross section for the 12Be(0+2) state reflects
the degree of the p-shell contribution for the two 0+ states in 12Be.!
• The different angular distributions of the cross sections suggest
a sensitivity to multipolarities.!

!

This study shows that spectroscopic studies
with the HIDCX reaction are a valid and feasible!

Thank you for your attention.

CountsBackup

12C(14C,14O)12Be!

12C(π+,π-)12OCounts

Elab=24A MeV

010

Ex
S. Mordechai et al.,!
PRC, 32 999 (1985)
20

30

25

20

15

10

50 Ex

W. !Oertzen et al.,!
NPA, 588 129c (1995)

11

Test Experiment to prove experimental feasibility
18O(12C,12Beγ)18Ne(gnd)Counts (A.U.)

Excitation EnergyCounts (A.U.)

Decay Time2γ time spectrum

12

decay timeFit

10

decay time constant: 395(+173-92) nsdecay time constant:
395+173-92 ns⇔ 331 ns in literature

818180160

1818O(12C,12Be) Ne w/o a -ray tag

w/o γ-tag

6418O(12C,12Be(0+)) Ne w/ a -ray tag × 10
218Ne(gnd)

140

yr
ani

120
100
80
60

200milBG
due to particleerpmis-identification

200

400

600

800

511keV

with γ-tag
×10t

40
12Be

200-20511keV-15-10-505101520
Ex (A.U.)1000 1200 1400
Time(ns)
Time[ns]