Inelastic scattering of 15 B and 17 B Y. Kondo A , T. Nakamura A , N. - - PowerPoint PPT Presentation

Inelastic scattering of 15B and 17B

• Y. Kondo A, T. Nakamura A, N. Fukuda B, T. Sugimoto A, M. Miura A, N. Aoi B, H. Baba C,
• D. Bazin D, T. Gomi C, H. Hasegawa C, N. Imai B, T. Kobayashi E, T. Kubo B, T. Motobayashi B,
• A. Saito C, H. Sakurai F, S. Shimoura G, K. Watanabe E, Y. X. Watanabe H, T. Yakushiji E,
• Y. Yanagisawa B, K. Yoneda D, and M. Ishihara B

A: Department of Physics, Tokyo Institute of Technology, Tokyo 152--8551, Japan B: RIKEN (Institute of Physical and Chemical Research, Saitama 351--0198, Japan C: Department of Physics, Rikkyo University, Tokyo 171--8501, Japan D: National Superconducting Cyclotron Laboratory, Michigan State University, Michigan 48824--1321, U.S.A E: Department of Physics, Tohoku University, Miyagi 980--8578, Japan F: Department of Physics, University of Tokyo, Tokyo 113--0033, Japan G: Center for Nuclear Study, University of Tokyo, Saitama 351--0198, Japan H: High Energy Accelerator Research Organization (KEK), Ibaraki 305--0801, Japan

Exotic features of neutron rich B isotopes

Neutron halo structure of 17B 15B

n n

• A. Ozawa et al. Phys. Lett. B, 334, 18, (1994).
• T. Suzuki et al. Nucl. Phys. A, 658, 313, (1999).
• T. Suzuki et al. Phys. Rev. Lett., 89, 12501, (2002).

Clustering structure

• Y. Kanada-En’yo and H. Horiuchi.
• Phys. Rev. C, 52, 647, (1995).

11B 13B 15B 17B 19B

Energy level of 15B

Experiment

[14] M. A. Hotchkis et al. Nucl. Phys. A398, 130, (1983). [15] T.S. Bhatia et al. Phys. Lett., 76B, 562, (1978). [13] R. Kalpakchieva et al. Eur. Phys. J. A, 7, 451, (2000).

13C(14C,12N)15B reaction

Theory

[16] N.A.F.M. Poppelier et al. Phys. Lett., 157B, 120, (1985). [17] E. K. Warburton and B. A. Brown.

• Phys. Rev. C, 46, 923, (1992).

[12] Y. Kanada-En’yo and H. Horiuchi.

• Phys. Rev. C, 52, 647, (1995).

No bound excited states of 15B are known. No excited states of 17B are known.

Inelastic scattering on C, Pb target

C(15B,15B*), Pb(15B,15B*), C(17B,17B*), Pb(17B,17B*)

☯ Energy of gamma ray

Excitation energy (Doppler shift should be corrected.)

☯ Ratio of cross section (σPb/σC)

Multipolarity 1- or 2+?

☯ Angular distribution (C target)

Multipolarity 1- or 2+? Deformation length (δ=βR)

Experiment

’ γ

E

15B 15B* 15B

C θ

Experimental setup

PPACs Drift chamber (FDC3) Dipole magnet Neutron counters (not used) Veto counters (not used) NaI(Tl) scintillators Drift chamber (FDC1) (not used) Secondary target (C, Pb) Hodoscope

15B,17B

73 Mev/u

15B,17B

Energy spectrum (C target)

(Doppler shift was corrected)

1.07 MeV 1.34 MeV

C(17B,17B*) C(15B,15B*)

These are the first observation. These correspond to the first excited states.

Observed gamma rays using C target

nuclide reaction This work Previous work

17B

C(17B,17B) 1.07(1)

15B

C(17B,15B) C(15B,15B) 1.34(1) 1.35(1)

14B

C(17B,14B) C(15B,14B) 0.652(2) 0.655(3) 0.740(40) [37]

12B

C(17B,12B) C(15B,12B) 0.953(4) 1.66(1) 0.957(4) 1.68(2) 0.95310(60) [38] 1.67352(60) [38] 0.95310(60) [38] 1.67352(60) [38]

[37] G. C. Ball et al. Phys. Rev. Lett., 31, 395, (1973). 14C(7Li,7Be)14B [38] H. H. Williams et al. Phys. Rev., 144, 801, (1966). 11B(d,p)12Bγ

Energy level of 15B and 17B

[16,17] shell model [12] AMD model (Clustering structure)

[40] G. Audi et al. Nucl. Phys. A, 624, 1, (1997).

Energy spectrum (Pb target)

Pb(15B,15B*) Pb(17B,17B*)

Cross section of inelastic scattering

15B 17B

σ(C) [mb] 17.0(1.1) 11.9(6) σ(Pb) [mb] < 190 < 160 σ(Pb) /σ(C) < 11 < 13

1- → σ(Pb) /σ(C) ～ 100 2+ → σ(Pb) /σ(C) ～ 2-3

UPPER LIMIT OF PEAK AREA

• O. Helene. Nucl. Instrum. Methods, 212, 319, (1983).

Angular distribution

Calculation using ECIS with assumptions 2+ transition Spin-parity of the excited state is 5/2- Collective excitation model → rotational model Optical potential (A: 12C-12C [24], B: 16O-12C [39])

[24] M. Buenerd et al. Nucl. Phys. A424, 313, (1984). [39] Maria-Ester Brandan. Phys. Rev. Lett., 60, 784, (1988).

Deformation length (δ＝βR)

Deformation length [fm]

15B 17B

Optical potential A 1.64(6) 1.35(3) Optical potential B 1.47(6) 1.24(2) δ（１５B）＞δ（１７B） The deformation of 15B seems to be larger than 17B.

Summary

Inelastic scattering on C, Pb target

C(15B,15B*), Pb(15B,15B*), C(17B,17B*), Pb(17B,17B*)

Gamma-ray energy

15B: EX = 1.34 MeV 17B: EX = 1.07 MeV 14B: EX = 0.65 MeV

Cross section ratio Angular distribution

2+ transition (mixing of 1+ transition is still unknown.)

Angular distribution

δ(15B) > δ(17B) Observed for the first time revised

Introduction

Neutron number Proton number H He Li Be C N O F Ne Na Mg Al stable neutron rich proton rich 8 8 20 B 2 2

15B, 17B

Vanishing of magic number N=8 Vanishing of magic number N=20 (Island of inversion)

15B

n n Neutron halo Clustering structure

In-beam gamma-ray spectroscopy

• ex. inelastic scattering of 15B

) 38 . ( = β ｃ ｖ β＝

＊

C target Eγ

Excited state

C

Θ’

’ γ

E

Ground state

15B 15B 15B β

projectile

Doppler correction

Lab frame

2 ' '

1 cos 1 β θ β

γ γ

− − = E E

Particle frame

15B

72 MeV/u 12 kcps

22Ne

110 MeV/u

Primary target (Be)

17B

73 MeV/u 0.8 kcps

RIPS （RIKEN Projectile-fragment Separator)

Plastic scintillator

Particle identification

Incident particle

TOF, pulse height (Z2/v2)

Outgoing particle

Z (charge)

TOF, pulse height (Z2/v2)

A (mass)

Rigidity (Av/Z), TOF, Z

Particle identification of incident particle

Particle identification of outgoing particle

Magnetic moment of B isotopes