1. Relativistic Coulomb excitation of nuclei near 100 Sn C.Fahlander, J. Eckman, M. Mineva, D. Rudolph, Dept. Phys., Lund University, Sweden M.G., A.Banu, A. Blazhev, H.Grawe, T.R.Saito, et al., GSI, Darmstadt, Germany J.Nyberg, et al., Dept. Rad. Sci., Uppsala University, Sweden B.Cederwall, et al., RIT, Stockholm, Sweden M.Bentley et al., Dept. Phys., Keele University, UK G.de Angelis, A. Gadea et al., LNL, Padova, Italy M.Palacz, et al., HIL, Warsaw University, Poland D.Sohler, et al., INR, Debrecen, Hungary P.Nolan, et al., Liverpool University, UK Surrey 29-30 March, 2004 RISING STOPPED BEAM PHYSICS WORKSHOP 100 Sn region studied with relativistic beams  B(E2: 2 + → 0 + )  structure of isomers

2. Experimental conditions  Fusion symmetric reaction EUROBALL, GASP + Ancillaries MSEP β decay  Fragmentation Coulex Isomers β decay → T. F. talk

3. Physics interest Shell structure SPE Residual Interaction E2 correlations Shell gap Core excitation: E2 E3 Magnetic rotation M1 bands E3 E2 I, E

5. Experimental Details 124 Xe, 700 AMeV  Primary beam: 124 Xe, 700 AMeV 9 Be, 4 g/cm 2  Production target: 9 Be, 4 g/cm 2 197 Au, 0.4 g/cm 2  Coulex target: 197 Au, 0.4 g/cm 2 108 Sn (58h), 112 Sn(28h), ~150 AMeV  Nuclei of interest: 108 Sn (58h), 112 Sn(28h), ~150 AMeV ~ 3-5 kHz intensity ~ 3-5 kHz intensity

6. Fragment identification projectile target outgoing A/Q Z 108 Sn before the target (FRS) Z A/Q Analysis in progress...

7. Simulated experimental spectra with realistic 108 Sn beam intensity and background including 2 + lifetime effects and estimated cross section Energy [keV] Counts Next step after succesful analysis, 106 Sn, 104 Sn (new proposal) pessimistic expected

8. 56 Ni and 100 Sn similarities 12 + : 76 Ni 8 + : 130 Cd 54 Fe

9. A. Blazhev et al., PRC submitted GDS: F.Nowacki, Nuc. Phys. A 704 (2002) 223c ESM: H. Grawe et al., NS98 AIP CP 481 (1999) 177 Core excited states in 98 Cd e π = 1.3(2) e π = 1.1

10. Shell Model calculations GDS 100 Sn shell gap: 12 + : πg 9/2 -2 νg 9/2 -1 (d 5/2,g 7/2 ) dominated by strong binding πg 9/2 -2 νg 9/2 -1 ≈ πg 9/2 -2 E(12 + )-E(8 + ) – measure of the shell gap EXP – SM = -325 keV for ESM (6.78 MeV) 6.46 MeV -34 keV for GSD (6.5 MeV) 6.47 MeV E sg = 6.46(15) MeV

11. Outlook:  E2 correlation Coulex  SPE structure and residual interaction isomers-stopped beam

12.  line shape in Sn isotopes  (2 + ) = 0.53 ps  short lifetime:  (2 + ) = 0.53 ps in 112 Sn  line shape of  transition depends on the projectile velocity   partial decay within thick target  velocity  uncertainty (0.452 0.497) MC simulations of  line shape lifetime dependency in 108 Sn: 142 AMeV 0.4 g/cm 2 0.5 ps 0.5 ps 0.2 ps 0.2 ps 0.1 ps 0.1 ps 1.0 ps 1.0 ps

14. Physics motivation  Insight into the structure of the 100 Sn nucleus  Information on shape vibrations of the doubly-magic core --- E2 core polarization effects  Unknown B(E2; 2 + 0 + ) values for light Sn isotopes (~1  s) e eff ( ) ~ 2.2e M.Lipoglavšek, et al., Phys. Lett. B 440 (1998) 246 6+6+ 102 Sn 0+0+ 2+2+ 4+4+ 48 497 1472 see Coulex on 108 Sn further step towards 100 Sn

15. Relativistic Coulomb Excitation of Nuclei Near 100 Sn Collaboration: Lund, Uppsala, Stockholm, Keele, Legnaro, Warsaw, Debrecen, Liverpool, Surrey, York, GSI Spokesperson: C. Fahlander, Lund University, M. Gorska, GSI Future experiments (next generation of RIB facility) will allow spectroscopy of 100 Sn. Closest neighbours to 100 Sn with measured excited states are 102 Sn and 98 Cd. Lifetimes and decay schemes of low- lying isomeric 6 + states in even Sn isotopes up to 102 Sn are known. Lipoglavsek et al. PLB 440 (1998) 246

16. At the catcher: ε p ~55% ε α ~10% ε n ~25% ε γ ~3.5% Prompt and delayed spectroscopy in 98 Cd 58 Ni + 46 Ti → 104 Sn * → 98 Cd + α2n 0+0+ 8+8+ 6+6+ 4+4+ 2+2+ 0 1395 2083 2281 2428 M.Górska et al., Phys. Rev. Lett. 79 (1997) 2415 R. Grzywacz et al., ENAM 98 AIP CP 455 (1998) 430

17. Identification

18. Coulex channel selection at ~150 AMeV Tracking  MW CATE target Scattering angles Event-by-event Doppler correction Tracking    p  1.6°  beam spot: 3  3 cm 2  1 step excitation ( M  = 1)   ,  event-by-event reconstruction reconstruction  impact parameter determination determination pp

19. Relativistic Coulex of 108 Sn 108 Sn 2 + 0 + only 10% of the data only 10% of the data w/o event-by-event tracking w/o event-by-event tracking w/o scattering angle selection w/o scattering angle selection

20. Summary and Outlook Coulomb excitation at relativistic energies Coulomb excitation at relativistic energies performed on 108,112 Sn nuclei performed on 108,112 Sn nuclei unambigously fragment identification before unambigously fragment identification before the target the target work on mass resolution in progress short lifetimes do not prevent the observation of the short lifetimes do not prevent the observation of the gamma peak gamma peak detailed analysis on event-by-event base in progress detailed analysis on event-by-event base in progress unique Z selection by CATE unique Z selection by CATE