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 measurements of 17 C and 19 N 2. 3. Summary Spin and Quantum Structure in Hadrons, Nuclei and Atoms (SQS04 at TIT)
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
The principle of β -NMR experiment : Asymmetry factor of β -ray emission A β : Polarization P
The principle of production for spin polarized RI beam from fragmentation reaction Momentum distribution of projectile fragments = P 0 p || The projectile fragment should be selected 1, in the momentum distribution 2, in the emission angle Emission angle
Production of spin polarized RI beam RIKEN Projectile-fragment Separator (RIPS) 22 Ne, 110 MeV/u RRC Detector setup to detect the spin polarization of RI
Confirmation of the spin polarization Adiabatic Field Rotation Method Beam pulsing & β -ray counting Spin- rotation 17 C, T 1/2 = 193(13)ms 19 N, T 1/2 =0.27(6) s Primary Beam Ne, 110 MeV/u Ne, 110 MeV/u Spin-pol. RI beam Momentum Target Nb, 778 mg/cm 2 nat C, 546 mg/cm 2 Acceptance Emission angle 2.3°～ 5.3° 2.6°～ 6.0° 17 C : 1.00 P 0 ± 3 % Momentum Accep. 7.21～7.66 GeV/c 8.18～8.69 GeV/c 19 N : 1.03 P 0 ± 3 % Stopper Pt ( at 75 K ) Pt ( at 15 K ) 370 Gauss 420 Gauss Bz A β P (net) -1.2 ±0.4 % 0.28 ±0.09 %
The β -NMR experiment for 17 C RF coil Adiabatic Fast Passage method ω 0 + ∆ ω ω 0 ω 0 − ∆ ω 40 ms Time ω 0 = γ Β 0 ( γ = µ N g / h ) Nuclear spin Effective Field
The β -NMR spectrum of 17 C | g ( 17 C g.s. ) |= 0.5054(24)
Spin parity assignment of 17 C I π =(1/2 + , 3/2 + , 5/2 + ) This experimental result J.P. Dufour, et al., Z. Phys. A 324 (1986) 487 I π ( 17 C) = 3/2 + PSDWBT 35% | π ( p 1/2 ) -2 ν ( d 5/2 ) 2 (2s 1/2 ) 1 > + MK MK3 31% | π ( p 1/2 ) -2 ν ( d 5/2 ) 3 > + …… E.K. Warburton and D.J. Millener, PSDMK Phys. Rev. C39 (1989) 1120 Similar result to PSDWBT
Spin parity of isotone N=11 Although I π ( 15 C, 19 C)=1/2 + , ε 2 ∼ 0.4 ε 2 ∼ 0.4 Deformation ? 17 C 19 O 21 Ne 23 Mg Nilsson diagram in prolate deformation region 16 C : deformed nucleus 1/2[211] β 2 = 0.93(21) 5/2[202] Recently reported by N. Imai in RIKEN 10 3/2[211] Phys. Rev. Lett. In print (2004) 1/2[220] Further research of 17 C will be needed. ε 2 : Quad. Deformation Ref. parameter ε 2 ~ 0.95 β 2 NPA 193 (1972)372 for 21 Ne NPA 140 (1970)333 for 23 Mg
Magnetic moment (n.m.) D C B A Deformation parameter ( ε 2 ) A : Bare g factor , κ = 0.08 B : Bare g factor, κ = 0.10 Effective g factor for 1 d orbit C : Effective g factor, κ =0.08 g s = -3.339, D : Effective g factor, κ =0.10 g l = -0.0749
The β -NMR experiment for 19 N Experimental Condition Graphite stopper at room • temperature This material was used in g -factor – measurement for 17 N. Beam Pulsing time : 50ms for beam • 700ms for β counting Beam Intensity : 5 kpps • β -ray yield : 500 cps • RF magnetic field : 10.0 [Gauss] • Counts / 2ms (log scale) T 1/2 = 298 ± 13 ms g = 0.58 ～ 0.64 ( 3.3 σ ) 0 100 200 300 400 500 600 700 Time for β -ray count (ms)
Magnetic moments of odd-mass Nitrogen Isotopes Conditions for 19 N in the calc. • Model Space : p, sd shell core : 4 He p -shell : 10~11 nucleons sd -shell : 4~5 nucleons • Bare g p , g n factor
Future perspective 95 MeV/nucleon 60 pnA Beam Intensity for spin-polarized RI Beam Target : Nb x 10 2 pps x 10 3 x 10 4 x 10 5 Program code : intensity_34 Island of Inversion
Summary • Confirmed Polarization for 17 C and 19 N produced from fragmentation reaction by using the new spin-flip method (Adiabatic Field Rotation) as 17 C : - 1.2 ± 0.4 % in Pt stopper at 75 K 19 N : 0.28 ± 0.09 % in Pt stopper at 15 K The g factor for 17 C and 19 N g.s. by using the b -NMR method as • 17 C g.s. : | g | = 0.5054 ± 0.0024 19 N g.s. : | g | = 0.58 ～ 0.64 (preliminary) • The assignment of spin parity for 17 C : I π ( 17 C) = 3/2 + Indication of the large deformation of 17 C Anomalous change of the g factor for 19 N compared with the shell • model predictions
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
The time spectrum of β -ray count Fitting function : N exp( - t / τ ) + Const. Counts / 2ms (log scale) Result : χ 2 = 1.002 T 1/2 = 298 ± 13 ms S/N = 4.5 The β -rays form daughter nuclei, 19 O(T 1/2 =26.91s), were treated as constant-background noise. 0 100 200 300 400 500 600 700 Half life of 19 N Time for β -ray count (ms) 1. The observed half life is consistent 2. with the value reported by P.L.Reeder in 1991. 3. 1. J.P. Dufour, et al,. Z. Phys. A 324 (1986) 487 4. 2. M. Samuel, et al., PRC 37 (1988) 1314 5. 3. J.P. Dufour, et al., AIP Conf. Proc. (1988) 344 4. P.L. Reeder, et al., PRC44 (1991) 1435 This exp. 5. Table of isotope 8 th edition Time (ms)
Shell model calculations • Model Space : p, sd shell p -shell : 11 nucleons sd -shell : 4 nucleons • Interaction : PSDMK, PSDWBT • g p , g n factor : bare The opposite sign of the off-diagonal M1 matrix element between the spin partner with d-orbital was found in PSDMK(WBP) and PSDWBT interaction.
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