108 Sn studied with intermediate-energy Coulomb excitation

1. 108Sn studied with intermediate-energy Coulomb excitation Dissertation zur Erlangung des Grades “Doktor der Naturwissenschaften” am Fachbereich Physik der Johannes Gutenberg-Universität in Mainz Leontina Adriana Banu

2. Outline • Motivation Why to study 108Sn ? Why to study it with Coulomb excitation ? • Experimental method description Most significant features of intermediate-energy Coulomb excitation • Experimental set-up • Data analysis • Experimental results • Theoretical interpretation

3. 100Sn N odd Z even Sn(N,Z) = B(N,Z) – B(N-1,Z) Number of protons (Z) Average energy of the first excited states in even- even nuclei Neutron separation energy [MeV] N=Z Number of neutrons (N) 2 8 50 20 28 82 126 • magic numbers shell closures 108Sn 112Sn Nuclear shell model 58 62 Why to study 108Sn ? • insight into the structure of 100Sn by • studying the nuclei in its vicinity • how rigid is the the doubly-magic core • when valence neutrons are being added ? • (studying A=102-130 Sn isotopes) • investigation on quadrupole polarization of • the doubly-magic core • (E2 core polarization effect) • B(E2;0+->2+)=|<f||OE2||i>|2 is the most • sensitive to E2 collective effects Z = 2,8,20,28,50,82 N = 2,8,20,28,50,82,126 • 100Sn (N=Z=50)principle test ground

4. Electromagnetic decay of lowest excited 2+state: () 2+ E 0+ lifetime transition probability Lifetime measurement ((E2) ~ B(E2)) Coulomb excitation B(E2) value 6+ cross section 253 4+ 905 2+ 1206 0+ 108Sn Why Coulomb excitation to study 108Sn ? 1207 keV 0 keV B(E2) value • B(E2) determination: ( ~ 7 ns) isomeric state 6+ E2 (< 0.5 ps) 2+ B(E2;6+->4+) = 3 W.u. E2 Z. Phys. A352 (1995) 373 (HI,xn) reaction

5. ( in our case ) Intermediate-energy Coulomb excitation Nuclear excitation ~ 3% E=1.3 MeV D = 70 cm n • Nuclear excitation (±) • Lorentz boost (+) • Doppler broadening (-) • Atomic background • radiation (-)  Coulomb excitation target  = 0.43 Detector opening angle Dq=3° Composite detector  = 0.57 DEg0/Eg0 [%]  = 0.43  = 0.11 1 Ge-Cluster detector qlab [deg]

6. SIS UNILAC FRS ESR GSI accelerator facility

7. Beam direction 124Xe @ 700 A•MeV CATE (Si) CATE (CsI) 9Be, 4 g/cm2 Experimental set-up Secondary beam @ reaction target: 108Sn/112Sn Primary beam (~ 150 A•MeV) • projectile fragmentation (production method) • in-flight fragment separation 197Au, 0.4 g/cm2 (Bρ-E-Bρ method)

8. 108Sn Fragment identification before/after target Selection with CATE Selection with FRS

9. rest in-flight 1 β 2 - E E 0 = γ γ 1 βcosΘ - γ Scattering angle measurement Beam tracking g CATE Target MW MW 511 keV Si CsI Qg  ~ 50% Qp 40K • Event–by–event Doppler shift correction: • Impact parameter determination:

10. Elastic scattering dominates Nuclear excitation contribution grazzing = 1.5° ± 0.5° Analysis of intermediate-energy Coulomb excitation • Fragment selectionbeforesecondary target • Fragment selectionaftersecondary target • Scattering angle selection (1°- 2°) • Prompt  time ‘window’ • Ge-Cluster multiplicity: M(E > 500 keV) = 1

11. I -particle coinc. • Measure: particle singles Np exp. theory 0.240 (14) e2b2 --- previous work B(E2; 0+ -> 2+) = 0.230 (57) e2b2 A. Banu et al., submitted to Phys. Rev. C (2005) Experimental results • Deduce B(E2) for 108Sn as follows:

12. theory (neutron valence and100Snas closed-shell core) theory (neutron valence+ proton core excitations and 90Zras closed-shell core) This work t=4 t=2 t=4 t=0 Neutron number B(E2 ) e2 b2 Theoretical interpretation Neutron/proton single-particle states in a nuclear shell-model potential: •••••••• Proton np-nh core excitations (t=n) & 100Sn core is open

13. Conclusion and Outlook • 108Sn the heaviest Z-nucleus studied with • intermediate-energy Coulomb excitation • B(E2;0+->2+) measured for the first time • The experimental result is in agreement • with latest large scale shell model calculations • This work brings more insight into the investigation of • E2 correlations related to 100Sn core polarization • 108Sn further step towards 100Sn

14. “Art is I, Science is We.” - Claude Bernard Thanks to… J. Gerl (GSI), J. Pochodzalla (Uni. Mainz) - thesis advisors C. Fahlander (Lund), M. Górska (GSI) - spokespersons H. Grawe, T.R. Saito, H.-J. Wollersheim (GSI) M. Horth-Jensen et al. (Oslo Uni.), F.Nowacki et.al (IRES) and last but not least…

15. The local RISING team Thank you...

16. Seniority scheme in Sn isotopes: 2 6+  = 0 4+ 2  = 0 2+ 2  = 2 0 0+ energy axis  jn J 6+ min  4+  j j j 2+ J J j j j j j J 0+ E(j2J) ~ V0tan(/2) for T=1, J even -residual interaction in a jn configuration (V12() = -V0(r1-r2))

18. Data Summary

19. Single-particle states in shell-model potential l -> orbital angular momentum Spectrsoscopic notation: l= 0, 1, 2, 3, 4, 5, 6 s, p, d, f, g, h, i •••••••• 2j+1 njl j -> total angular momentum j = l + s j = l ± ½ s = 1/2 2j+1 nucleons /orbital inert core + active valence nucleons

20. j -> total angular momentum j = l + s j = l ± ½ s = 1/2 Single-particle states in shell-model potential l -> orbital angular momentum Spectrsoscopic notation: l= 0, 1, 2, 3, 4, 5, 6 s, p, d, f, g, h, i 2j+1 njl 2j+1 nucleons /orbital

21. Generalized seniority scheme: B(E2;0+ -> 2+) ~ f(1-f)where f = (N – 50)/ 32