Quadrupole collectivity in neutron-rich Cd isotopes

1. Quadrupole collectivity in neutron-rich Cd isotopes Thorsten Kröll for the IS411/IS477/IS524 collaborations Work supported by BMBF (Nr. 06DA9036I and 05P12RDCIA), EU through EURONS (No. 506065) and ENSAR (No. 262010), HIC for FAIR, and the MINIBALL/REX-ISOLDE

2. N=82 132Sn Z=50 Sn Z=50 ¬ ­ Z=48 Cd r process 122,123,124,126,128Cd Region of interest 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 2

3. Neutron-rich Cd isotopes • E(2+) drops from 126Cd to 128Cd! • Not reproduced by SM • Beyond Mean Field* approach with • Gogny D1S force • angular momentum projection • particle number projection • configuration mixing (GCM) • Þ • trend of E(2+) reproduced • E(2+) somewhat too large • 128Cd is prolate deformed!?! Data: nndc.bnl.gov W. Watanabe et al., PRL 111, 152501 (2013) *T. R. Rodríguez et al., Phys. Lett. B668, 410 (2008) 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 3

4. Experimental set-up MINIBALL Beams from REX-ISOLDE @ »2.85 MeV/u MINIBALL DSSSD • 24 6-fold segmented • HPGe detectors (e ≈ 7%) • fully digital electronics • N. Warr et al., EPJ A 49, 40 (2013) • “Safe” Coulomb excitation • Gamma – particle coincidences • Isobaric beam contaminants 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 4

5. Prompt g-ray spectra NEW • 646 keV is indeed the 2+à 0+ transition in 128Cd!!! • Coulomb excitation of isobaric In contamination • - level scheme of 126In needs revision A. Scherillo et al., PRC 70, 054318 (2004) • - new SM calculations agree with finding (G. Simpson, UWoS) • - conversion electron measurement (August 2013 @ ILL) ... analysis ongoing Analysis of 128Cd/128In: Sabine Bönig (PhD thesis, TU Darmstadt, 2014) 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 5

6. Analysis procedure • “safe” Coulomb excitation ... single step dominates • reorientation effect .... quadrupole moments 2+ 0+ 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 6

7. Maximum likelihood fit • find optimal M20-M22 combination • if available, additional information like lifetimes is included • projection of 1s contour on axes without t Lifetime measurement with DSAM Michael Thürauf (Master thesis, TU Darmstadt) 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 7

8. New beyond mean field calc‘s • Beyond mean field including triaxiality • prolate deformation (g ≈ 0) • excitation energies better reproduced • large overlap of wave functions • ... large B(E2) Tomás Rodriguez (TU Darmstadt) 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 8

9. p p Collectivity in even Cd isotopes 122,124,126Cd S. Ilieva et al., PRC 89, 014313 (2014) u • experimental B(E2) value for 128Cd robust (different conditions in analysis) • general trend for even Cd isotopes continued • - larger B(E2)’s than SM prediction • - B(E2)’s well reproduced by BMF • - very limited sensitivity to Q2 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 9

10. 123Cd – first odd Cd isotope • Coulomb excitation of both 123Cd and 123mCd • Level scheme of 123Cd well known in literature ...??? DC wrt projectile DC wrt target recoil (unresolved multiplet) Anna-Lena Hartig (Master thesis, TU Darmstadt, 2014) 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 10

11. 123Cd – revised level scheme Inconsistencies with literature H. Huck et al., PRC 40, 1384 (1989) ... revised level scheme (... mainly single-step excitations!!!) - g-ray yield following Coulomb excitation - gg coincidences ... very few - variation of 123Cd/123mCd content in beam (RILIS, only broad band laser available for this run) Matrix elements, e.g. 117 keV: 0.92 eb 376 keV: 0.50 eb ... similar size 222 598 376 412 Excitation energy of isomer: 144 keV (not 316 keV) A. Kankainen et al., PRC 87, 024307 (2013) 466 117 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 11

12. and thank you for your attention!!!! Summary and Outlook • Safe Coulomb excitation of even neutron-rich isotopes 122,124,126,128Cd • ... B(E2) values are larger than predictions from large scale SM calculations • ... better agreement with BMF ... axially symmetric shapes • ... no clear conclusion from Q2(2+) values ... small deformation preferred • First successful run with odd isotope 123Cd • ... level scheme needs revision ... new decay experiment desirable • ... both positive and negative parity orbitals seem to contribute similarly • to collectivity • Continuation of programme at HIE-ISOLDE • ... multiple Coulomb excitation • ... lifetime measurements with plunger • ... 130Cd (... worth a try at HIE-ISOLDE?) • ... narrow band laser to ionise selectively g.s. or 11/2- isomer in odd isotopes • ... transfer reactions to pin down single-particle properties 1-6 June 2014 | ARIS 2014 - Tokyo | Institut für Kernphysik, TU Darmstadt | Thorsten Kröll | 12