CNS, Univ. of Tokyo MATSUSHITA Masafumi ガンマ線核分光で探る不安定核の殻構造進化 Sep 第３回 RIBF 討論会

Experiments by means of in-beam  ray spectroscopy. Experiments by means of in-beam  ray spectroscopy. γ -ray Spectroscopy Setup at RIBF

PID of projectile particles PID of ejectile particles Determine reaction channel and correct Doppler shift effects. Observables: velocity  emission angle  -ray energy Observables: velocity  emission angle  -ray energy γ -ray Spectroscopy Setup at BigRIPS / ZDS

Arrangement Hedgehog like Size (cm 3 )4.5 x 8 x 16 # of Detectors160 Volume~ 90 liter # of Layers16 Angular resolution~ 8 degree Energy resolution (  ~0.6) 1MeV Efficiency (  ~0.6) (  ~0.3)) Timing resolution~ 2.5ns (FWHM) Ref. S.Takeuchi et al., RIKEN Accel. Prog. Rep. 36(2003)148 Ex.) S.Takeuchi et al., PRC 79, (2009) Standard specification  -ray energy Emission angle of  ray  For Doppler-shift corrections Detector Array for Low Intensity radiation DALI2 for RIBF Experiments

2008DayOne 32 Ne, 31,33 NaH. Scheit, P. Doornenbal PRL 103:032501, 2009./PRC 81:041305, Test with U ( pnA) ~ 132 SnH. Wang, N. Aoi Ca campaign 38,40,42 SiS. Takeuchi, M.Matsushita submitted to PRL A>36 MgP. Doornenbal, H. Scheitin preparation F isotopesP. Doornenbalin preparation ~Al, PD. Steppenbeckin preparation 33 MgD. Bazin 40 Mg test P. Fallon 2011U beam campaign 78 NiK. Yoneda, D. Steppenbeck ~ 132 SnH. Wang, N. Aoi Xe and 70 Zn beam campaign 10x SnA. Obertelli, P. Doornenbal 54 CaD. Steppenbeck, S. Takeuchi In-beam γ -ray spectroscopy at RIBF

Landscape on and around “ Island of inversion ” Large collectivity (B(E2)) Large collectivity (E x (2 + )) Deformed (R42)

2 + state in 32 Ne - DayONE experiment (2008) -

Landscape on and around “ Island of inversion ” Large collectivity (B(E2)) Large collectivity (E x (2 + )) Deformed (R42)

Spectroscopy of 36,38 Mg P.Doornenbal et al

Landscape on and around “ Island of inversion ” Large collectivity (B(E2)) Large collectivity (E x (2 + )) Deformed (R42)

Inconsistent results between two-proton removal reactions, 44 S  42 Si NSCL case  A substantial Z=14 subshell closure J.Fridmann et al., Phys. Rev. C 74, (2006) GANIL case  Well-deformed oblate rotor B.Bastin et al., Phys. Rev. Lett. 99, (2007). Inconsistent results between two-proton removal reactions, 44 S  42 Si NSCL case  A substantial Z=14 subshell closure J.Fridmann et al., Phys. Rev. C 74, (2006) GANIL case  Well-deformed oblate rotor B.Bastin et al., Phys. Rev. Lett. 99, (2007). Re-visit 42 Si to confirm the 2 + excitation energy Determine the location of the 4 + state in 42 Si (and other Si isotopes) Re-visit 42 Si to confirm the 2 + excitation energy Determine the location of the 4 + state in 42 Si (and other Si isotopes) S.Takeuchi, M.M et al., submitted to PRL. What we know about 42 Si Z=14 N A R(4/2) Ex (MeV) ? 2+2+ (4 + ) ?

 ray ( 2 +  0 + ): 742(8) keV new lines: 1431(11) keV 2032(9) keV 2357(15) keV  ray ( 2 +  0 + ): 742(8) keV new lines: 1431(11) keV 2032(9) keV 2357(15) keV *Widths are fixed to simulated values. 44 S + C  42 Si +  + X GANIL exp. : 770(19) keV B.Bastin et al., Phys. Rev. Lett. 99, (2007). We confirmed  line observed at GANIL. GANIL exp. : 770(19) keV B.Bastin et al., Phys. Rev. Lett. 99, (2007). We confirmed  line observed at GANIL. 42 Si : 2 + peak with high statistics

*Widths are fixed to simulated values. 44 S + C  42 Si +  + X 42 Si : 2 + peak with high statistics Excited state at 2173(14) keV has been tentatively assigned to the 4 + state from present study keV 2239 keV g.s. 42 Si

Other isotopes : 38,40 Si 38 Si 40 Si

Other isotopes : 38,40 Si E x (4 + )/E x (2 + ) = 2.09 E x (4 + )/E x (2 + ) = 2.56

Low 2 + excitation energy R(4/2) = 2.93: well deformed Development of deformation toward N=28  indicate disappearance of N=28 Low 2 + excitation energy R(4/2) = 2.93: well deformed Development of deformation toward N=28  indicate disappearance of N=28 Systematic in Si isotopes T.Otsuka et al., NPA 805 (2008) 127c Y.Utsuno et al., arXiv/ (2012) -- without tensor force ― with tensor force Present exp.

Landscape on and around “ Island of inversion ” Large collectivity (B(E2)) Large collectivity (E x (2 + )) Deformed (R42)

RIKEN:S.TAKEUCHI, N.AOI, P.DOORNENBAL, J.LEE, L.KUOANG, H.SCHEIT, D.STEPPENBECK, H.WANG, T.MOTOBAYASHI, H.SAKURAI, H.BABA, M.TAKECHI, Y.TOGANO, K.YONEDA, M.MATSUSHITA TITech:N.KOBAYASHI, G.LEE, Y.KONDO, T.NAKAMURA, T.SAKO, K.TAKAHASHI CNS:S.GO, E.IDEGUCHI, S.MICHIMASA, S.OTA, S.SHIMOURA TU München:R.GERNHAEUSER, C.HINKE, R.KRUCKEN, K.STEIGER ANL:C.HOFFMAN GANIL:L.CACERES Frankfurt/GSI:T.L.BLEIS IN2P3:S.GREVY, A.MATTA LBNL:H.CRAWFORD, P.FALLON, M.PETRI, LPC CAEN:J.GIBELIN NSCL:D.BAZIN, R.WINKLER RICHMOND:R.HUGHES YORK:D.JENKINS THANK YOU FOR YOUR ATTENTION Collaborators