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Nuclear moment studies with spin polarized radioactive beams from fragmentation reaction Daisuke Kameda Department of Physics, Tokyo Institute of Technology Plan of the talk 1. Introduction of the nuclear-moment measurement g factor

SLIDE 1

Nuclear moment studies with spin polarized radioactive beams from fragmentation reaction

Daisuke Kameda Department of Physics, Tokyo Institute of Technology Plan of the talk 1. Introduction of the nuclear-moment measurement 2. g factor measurements of 17C and 19N 3. Summary Spin and Quantum Structure in Hadrons, Nuclei and Atoms (SQS04 at TIT)

SLIDE 2

Nuclear-moments measurement around light mass region by using the spin-polarized Radio Isotope (RI) beam

H. Ogawa et al.,

Phys.Rev. C 67 (2003) 064308

µ l, j of the valence orbital Q effective charge, deformation

SLIDE 3

The principle of β-NMR experiment

Aβ : Asymmetry factor of β-ray emission P : Polarization

SLIDE 4

The principle of production for spin polarized RI beam from fragmentation reaction

p||

Emission angle Momentum distribution of projectile fragments The projectile fragment should be selected 1, in the momentum distribution 2, in the emission angle

= P0

SLIDE 5

Production of spin polarized RI beam

RIKEN Projectile-fragment Separator (RIPS)

RRC

Detector setup to detect the spin polarization of RI

22Ne, 110 MeV/u

SLIDE 6

Confirmation of the spin polarization

Beam pulsing & β -ray counting

Spin- rotation

Adiabatic Field Rotation Method

17C,T1/2 = 193(13)ms 19N,T1/2=0.27(6) s

Primary Beam Ne, 110 MeV/u Ne, 110 MeV/u Target Nb, 778 mg/cm2

natC, 546 mg/cm2

Bz 370 Gauss 420 Gauss Aβ P (net)

1.2 ±0.4 %

0.28 ±0.09 % Emission angle 2.3°～ 5.3° 2.6°～ 6.0° Momentum Accep. 7.21～7.66 GeV/c 8.18～8.69 GeV/c Stopper Pt ( at 75 K ) Pt ( at 15 K ) Spin-pol. RI beam Momentum Acceptance

17C : 1.00 P0 ± 3 % 19N : 1.03 P0 ± 3 %

SLIDE 7

The β-NMR experiment for 17C

Effective Field Nuclear spin ω0 − ∆ω ω0 + ∆ω

ω0 Adiabatic Fast Passage method ω0 = γ Β0 ( γ = µN g / h )

RF coil

40 ms

Time

SLIDE 8

The β-NMR spectrum of 17C

|g (17Cg.s.) |= 0.5054(24)

SLIDE 9

Spin parity assignment of 17C I π (17C) = 3/2+

This experimental result

E.K. Warburton and D.J. Millener,

Phys. Rev. C39 (1989) 1120

MK MK3 J.P. Dufour, et al., Z. Phys. A 324 (1986) 487

I π =(1/2+, 3/2+, 5/2+)

PSDWBT 35% | π(p1/2)-2 ν(d5/2)2(2s1/2)1 > + 31% | π(p1/2)-2 ν(d5/2)3 > + …… PSDMK Similar result to PSDWBT

SLIDE 10

3/2[211] 5/2[202] 1/2[220] 1/2[211]

ε 2 : Quad. Deformation

parameter

ε 2 ~ 0.95 β 2

17C 19O 21Ne 23Mg

ε2 ∼ 0.4 ε2 ∼ 0.4

Spin parity of isotone N=11

Although I π(15C, 19C)=1/2+ ,

Nilsson diagram in prolate deformation region

16C : deformed nucleus

β 2 = 0.93(21)

Recently reported by N. Imai in RIKEN

Phys. Rev. Lett. In print

(2004) Deformation ?

Further research of 17C will be needed.

Ref. NPA193(1972)372 for 21Ne NPA140(1970)333 for 23Mg

SLIDE 11

Deformation parameter (ε2 ) Magnetic moment (n.m.) B A C D

A : Bare g factor , κ = 0.08 B : Bare g factor, κ = 0.10 C : Effective g factor, κ=0.08 D : Effective g factor, κ=0.10 Effective g factor for 1d orbit gs = -3.339, gl = -0.0749

SLIDE 12

The β-NMR experiment for 19N

Experimental Condition

Graphite stopper at room

temperature

– This material was used in g-factor measurement for 17N.

Pulsing time : 50ms for beam

700ms for β counting

Beam Intensity : 5 kpps
β-ray yield : 500 cps
RF magnetic field : 10.0 [Gauss]

Beam

0 100 200 300 400 500 600 700

Time for β-ray count (ms) Counts / 2ms (log scale) T1/2 = 298 ± 13 ms

g = 0.58～0.64 (3.3 σ )

SLIDE 13

Magnetic moments of odd-mass Nitrogen Isotopes

Conditions for 19N in the calc.

Model Space : p, sd shell

core : 4He p-shell : 10~11 nucleons sd-shell : 4~5 nucleons

Bare gp, gn factor

SLIDE 14

Future perspective

x 10 2 x 10 3 x 10 4 x 10 5 pps

95 MeV/nucleon 60 pnA

Beam Intensity for spin-polarized RI Beam Program code : intensity_34 Target : Nb Island of Inversion

SLIDE 15

Summary

Confirmed Polarization for 17C and 19N produced from fragmentation reaction

by using the new spin-flip method (Adiabatic Field Rotation) as

17C : - 1.2 ±0.4 % in Pt stopper at 75 K 19N : 0.28 ±0.09 % in Pt stopper at 15 K

The g factor for 17C and 19Ng.s. by using the b-NMR method as

17Cg.s. : |g | = 0.5054 ±0.0024 19Ng.s. : |g | = 0.58 ～ 0.64 (preliminary)

The assignment of spin parity for 17C : I π (17C) = 3/2+

Indication of the large deformation of 17C

Anomalous change of the g factor for 19N compared with the shell

model predictions

SLIDE 16

Acknowledgements

K. Asahi, H. Ogawa, H. Miyoshi, K. Shimada, G. Kato, S. Emori,
G. Kijima, T. Suga, K. Ohno, K. Yogo, K. Sakai

Department of Physics, Tokyo Institute of Technology

H. Ueno, A. Yoshimi, H. Watanabe, T. Haseyama, Y. Kobayashi,
W. Sato, K. Yoneda, J. Murata, A. Yoshida, T. Kubo,

and M. Ishihara The Institute of Physical / Chemical Research, RIKEN

N. Imai

Department of Physics, The University of Tokyo

SLIDE 17

The time spectrum of β-ray count

Fitting function : N exp( -t/τ ) + Const. Result : χ2 = 1.002 T1/2 = 298 ± 13 ms S/N = 4.5

The β-rays form daughter nuclei,

19 O(T1/2=26.91s), were treated as

constant-background noise.

The observed half life is consistent with the value reported by P.L.Reeder in 1991. Half life of 19N

Time (ms) This exp.

1. J.P. Dufour, et al,. Z. Phys. A324 (1986) 487 2.

M. Samuel, et al., PRC37 (1988) 1314

3. J.P. Dufour, et al., AIP Conf. Proc. (1988) 344 4. P.L. Reeder, et al., PRC44 (1991) 1435 5. Table of isotope 8th edition

1. 2. 3. 4. 5.