1. H.Sakurai Univ. of Tokyo Spectroscopy on light exotic nuclei

2. RIKEN Facility RIKEN Ring Cyclotron Experiment RIPS (Riken Projectile Fragment Separator) production target In-flight RI beam production Primary beam E/A~64-135 MeVRI beam E/A~30-90 MeV K=540

3. Progress of Research Opportunities with RI Beams Construction of a dedicated facility for RI beam production via the projectile fragmentation

4. SRC K=2500 350~400 A MeV 350A MeV U

5. present facility RI beams A < 50 E ~ 50A MeV RIBF RIPS RIBF RI beams A < 200 E ~ 250A MeV RIBF RI Beam Factory : the 3 rd generation facility in 2007

6. - “Magicity Loss” and Collective Motion - Investigation on Nuclear Structure via In-beam  Spectroscopy

7. Experimental setup for in-beam gamma spectroscopy with fast RI beams RI beam gamma-ray detector array Charged particle detectors target particle identification for ejectiles NaI detector Doppler-shift corrected spectrum ~50 A MeV observation of de-excited  rays  -ray energy and emission angle for Doppler correction γ beam θ E 2+2+ 0+0+ γ inverse reaction high energy beam -> thick target kinematical focusing -> high efficiency

8. - “Magicity Loss” and Collective Motion - Present Facility RIPS 1. Magicity loss at N~20 2. 16 C The New Facility RIBF 3. Future Investigation on Nuclear Structure via In-beam  Spectroscopy

9. Investigation for the island-of-inversion region 20 8 28 34 Mg 30 Ne 32 Mg Search for new isotopes Particle stability 31 Ne, 31 F … In-beam gamma spectroscopy B(E2) <- CEX 32 Mg, 34 Mg E(2 + ), E(4 + ) <- Two step fragmentation 34 Mg How is the region extended ? lower Z and larger N 27 F 31 F proton inelastic scattering 30 Ne E(2 + ) 27 F bound excited states 34 Mg has a larger collectivity than 32 Mg. Why 31 F is particle bound ? How large collectivity at Z=9, 10? In-beam gamma spectroscopy

10. The first excited state of 30 Ne via (p,p’) Yanagisawa et al., Phys. Lett. B 566 (2003) 84 0h  2h  30 Ne 32 Mg 34 Si 36 S N=20 Isotone E(2 1 + ) [keV] data 885791 Luminosity Enhancement via Liquid Hydrogen target 30 Ne Intensity ~ 0.2 /sec Number of target nuclei p Pb 200 : 1 Counts/40keV Energy [keV] 29 Ne 28 Ne ~200 mg/cm 2 E(2 +, 30 Ne) < E(2 +, 32 Mg) 30 Ne has a larger collectivity than 32 Mg?

11. Elekes et al., PLB 599 (2004) 17 Bound excited states in 27 F Sn=1.4 MeV 27 F 1.1 2.0 5/2 + 1/2 + sdpf sd Otsuka et al. Brown Two bound excited states for 25,26,27 F via p( 27 F, 25,26,27 F  ) proton contribution across Z=8 gap?? One bound excited state predicted via sdpf-shell model <- neutron excitation across N=20

12. - “Magicity Loss” and Collective Motion - Present Facility RIPS 1. Magicity loss at N~20 2. 16 C The New Facility RIBF 3. Future Investigation on Nuclear Structure via In-beam  Spectroscopy

13. unstable nuclei lifetime Coul. Ex. Z<8 10 Be 12 Be 14 Be 12 C 14 C 16 C 18 C 20 C 22 C 16 O 18 O 20 O 22 O 24 O 20 Ne 22 Ne 24 Ne 26 Ne 28 Ne 30 Ne 32 Ne 34 Ne 24 Mg 26 Mg 28 Mg 30 Mg 32 Mg 34 Mg 36 Mg 38 Mg 28 Si 30 Si 32 Si 34 Si 36 Si 38 Si 40 Si B(E2) measurement for the light mass region stable nuclei No data for the neutron-rich Be and C isotopes B(E2)  CEX Z<8 Coulomb Ex. < Nuclear Ex.

14. Density distribution of the C isotopes by AMD proton neutron proton neutron Y. Kanada-En’yo and H. Horiuchi, Prog. Theor. Phys. 142,205(2001)

15. unstable nuclei lifetime Coul. Ex. Z<8 10 Be 12 Be 14 Be 12 C 14 C 16 C 18 C 20 C 22 C 16 O 18 O 20 O 22 O 24 O 20 Ne 22 Ne 24 Ne 26 Ne 28 Ne 30 Ne 32 Ne 34 Ne 24 Mg 26 Mg 28 Mg 30 Mg 32 Mg 34 Mg 36 Mg 38 Mg 28 Si 30 Si 32 Si 34 Si 36 Si 38 Si 40 Si B(E2) measurement for 16 C via a new techniques stable nuclei B(E2) Lifetime measurement of 2 + state New method appropriate for fast RI beam should be developed “Recoil-Shadow-Method” Z<8 Coulomb Ex. < Nuclear Ex. ~  2+2+ 0+0+ CEX

16. Inelastic Scattering of RI beams High velocity (  )   =  c ~ 1.0 cm (  =100ps,  =0.3) Thick lead shield  “shadowing” for  -rays in delayed emission  = exp (-  l )  : attenuation coeff.  l : path length in lead target ( 9 Be) Recoil-shadow-method R1, R2 gamma detectors R1/R2 ratio has mean life dependence

17. B(E2) /B(E2)sys=0.03 Anomalously hindered B(E2) of 16 C B(E2: 2 + -> 0 + ) B(E2)sys=6.47Z 2 A -0.69 E(2 + ) -1 Quantum liquid drop model 0.63 [e 2 fm 4 ] 0.26 [W.u.] S. Raman et.al.,PRC37, 805 (‘88).  = 77 +/- 14 (stat.) +/- 19 (syst.) [ps] N. Imai et al, Phys.Rev.Lett. 92,062501(‘04)  em = 0.14

18. Neutron contribution to the 2 + state??

19. Proton Inelastic Scattering on 16 C H.J. Ong et al, to be submitted to PRL proton: the most sensitive probe for neutron matter In-beam  technique to obtain angular integrated cross section  = 24 +/- 4 mb DWBA analysis (ECIS)  pp’ = 0.50 +/- 0.07 >  em =0.14  pp’ = 1.42 +/- 0.21 fm Errors include optical potential dependences (CH89, p+ 12 C, p+ 16 O), too 102050100200 mass number A  pp’ /  sys  pp’ /  sys ~1 16 C  sys = 466A -1 E(2 + ) -1/2 Raman’s systematics Magnitude of  pp’ for 16 C is the same as those of other nuclei. Neutron-dominant collective motion

20.  n /  em =| M n /M p |/ (N/Z) = 4.0 +/- 1.4 102050100200 mass number A 1.Combination of  em and  pp’, based on Bernstein’s prescription Disentanglement of proton and neutron contributions M n /M p / (N/Z) H.J. Ong et al, to be submitted to PRL  em B(E2  )=0.28(6) [W.u.] 2. Interference of nuclear and Coulomb excitation in inelastic scattering on Pb Elekes et al., Phys.Lett.B 586, 34 (2004)  n /  em =4.6 +/- 1 Imai et al. B(E2  )=0.26 [W.u.]

21. New type of collective motion? TWO quantum liquid drops “exotic” picture for 16 C case proton matterneutron matter Large contribution by neutron matter, not by proton matter  n /  em =4 ~ 5 ONE quantum liquid drop proton- and neutron matter’s contributions to collective motion are same. “classical” picture one-body nuclear matter

22. Why B(E2) is so small?? Z=6 magic number ? Effective charges ? Shell gaps from mass information proton-shell ~ 12 MeV a large gap between p3/2 and p1/2 neutron-shell < 1 MeV e n /e ~ 0 due to weak binding of neutrons? Q-moments of 15,17 B Izumi et al., PLB366 (1996)51 Ogawa et al., PRC67(2003)064308 Based on Audi et al., NPA 729(2003)337

23. Proton and neutron shell gaps from mass information neutron number proton number proton shell gap S2p(Z,N)-S2p(Z+2,N) neutron shell gap S2n(Z,N)-S2n(Z,N+2) 16 C MeV Z=6 N=10 H.Sakurai ENAM04 p1/2 p3/2 p1/2s1/2d5/2

24. - “Magicity Loss” and Collective Motion - Present Facility RIPS 1. Magicity loss at N~20 2. 16 C The New Facility RIBF 3. Future Investigation on Nuclear Structure via In-beam  Spectroscopy

25. Exploration towards heavier and more proton-rich /neutron-rich region to produce a lot of data for “unified pictures” RIBF RIPS

26. 50 82 126 28 20 B(E2) -1 [1/W.u] neutron number proton number 132 Sn 208 Pb 78 Ni double magicity? N=34 new magicity? N=28 magicity? N=82 magicity? deformation region? 48 Ni double magicity? 100 Sn double magicity? Subjects of nuclear structure and collectivity 2001 CEX -> B(E2) (p,p’) ->  2

27. neutron skins ? collectivity originated from neutrons in skin pairing ? rotation energy v.s. pairing energy exotic modes ? originated from two asymmetric liquids... Higher excited states and higher spin states for exotic phenomena of collectivity? not only low lying states but also... J, Ex for intermediate and heavy mass system

28. Summary Anomalous quadrupole collectivity of 16 C proton matterneutron matter neutron-dominant collectivity How about 18 C, 20 C … ? B(E2), (p,p’), Interference  n /  em = 4~5 > 1 Island of inversion 30 Ne E(2 +, 30 Ne) < E(2 +, 32 Mg) 30 Ne has a larger collectivity than 32 Mg? 27 F two bound excited states. proton contributions across Z=8? For future Any exotic collective motion proposed in medium- and heavy-mass region?