Observation of new neutron-deficient isotopes with Z ≥ 92 in multinucleon transfer reactions

1. Observation of new neutron-deficient isotopes with Z ≥ 92 in multinucleon transfer reactions Sophie Heinz GSI Helmholtzzentrum and Justus-Liebig-Universität Gießen ECT* Trento, September 1 – 4, 2015

2. Fusion, Fragmentation and Fission ? Deepinelastic Transfer Figure: courtesy R. Knöbel

3. Deep Inelastic Reactions of Heavy Ions E* = Ecm – TKE + Q FUSION Compound Nucleus QUASIFISSION Primary Products (PP) Evaporation Residue (ER) Fission Fragments σER = σcap ∙ PPP ∙ Psurvival →σ<< 1 μb for new exotic heavy nuclei The small cross-sections require separation + single event detection

4. 1 E, T1/2 2 E, T1/2 3 E, T1/2 sf The Velocity Filter SHIP at GSI Separation and identification of heavy reaction products at SHIP pulsed beam structure Ndetector≈ 100 / s 5 ms 15 ms Nbeam≈ 5·1012 / s Isotope identification via α decay chains v ~ E/B ΔΘ = (0 ± 2)°; ΔΩ = 10 msr

5. 1 E, T1/2 2 E, T1/2 3 E, T1/2 sf The Velocity Filter SHIP at GSI Separation and identification of heavy reaction products at SHIP Very sensitive method pulsed beam structure Ndetector≈ 100 / s 5 ms σ1 event ≈ 50 pb T1/2 ≥ 20 μs low limit cross-sections: 15 ms Nbeam≈ 5·1012 / s Isotope identification via radioactive decays access to short-living nuclei: v ~ E/B ΔΘ = (0 ± 2)°; ΔΩ = 10 msr

6. Velocity Spectra of DIT products at θ = 0º compound nucleus elastically scattered target ions transfer products yield v / vcm Compound nucleus velocity: Elastically scattered target ions:

7. Velocity and Bρ Spectra Example: Ca + Cm elastically scattered target ions compound nucleus

8. Transfer Products from 48Ca + 248Cm Theoretical model calculations for 48Ca + 248Cm → V. Zagrebaev and W. Greiner Ecm = 210 MeV (= 1.05 VCoulomb) cross-section (mb) primary TP excitation energy (MeV)

9. 48Ca + 248Cm Reactions at SHIP E = 225 MeV ( = 1.12 Vcoulomb) alpha spectrum measured at a setting for target-like quasi-fission products → beam-off condition

10. Identified Isotopes → First synthesis of new heavy isotopes in DIT reactions H.M. Devaraja et al., „Observation of new neutron-deficient isotopes with Z ≥ 92 in multinucleon transfer reactions“, accepted for publication in Phys. Lett. B

11. Example: New Isotopes of 95Am and 97Bk Observed decay chains

12. Isotopic distributions ► measured isotopic distributions are located ~5 neutrons left from the expected primary distributions → ~5 neutrons are evaporated from the PTP → E* (PTP) ≈ 50 MeV → for target-like TP with Z = 86 – 92

13. Energy dissipation Total kinetic energy: TKE = Ecm – E* + Q = Ecm – TKEL TKE goes below the Viola energy of a fissioning compound nucleus → this reflects the quasi-fission process

14. Comparison of DIT and Fusion Reactions Cross-sections of uranium isotopes from transfer and fusion 92U ► Systematic uncertainties: estimated up to factor 10 for fusion and DIT

15. Summary ► DIT reactions are heavily discussed as a means to produce new isotopes in the region of superheavy nuclei and N ≈ 126 nuclei ► Recently we observed for the first time new neutron-deficient Z ≥ 92 nuclei using the velocity filter SHIP at GSI → σ1 event ~50 pb → selection of DIT products from central collisions with low angular momenta ► Cross-sections of the new isotopes: σ ~ (1 – 10) nb → comparable to fusion cross-sections in this region but: DIT reactions populate vast region of nuclei in the same experiment ► Are DIT reactions favourable for production of (super)heavy nuclei? ● Z > 92, N ≈ 126 → DIT appears favourable ● Z < 82, N ≈ 126 → Fragmentation appears favourable (O. Beliuskina et al., Eur. Phys. J. A 50, 161 (2014)) ● N-rich SHN → DIT very difficult: tiny σ and missing ID methods

16. DIT for the N ≈ 126, Z < 82 region? DIT reactions in 64Ni + 207Pb Transfer and fragmentation cross-sections for neutron-rich nuclei: σTransfer ≥ σFragmentation − O. Beliuskina et al., Eur. Phys. J. A 50, 161 (2014). − [1] W. Krolas et al., Nucl. Phys. A 724 (2003) 289.

17. DIT for the N ≈ 126, Z < 82 region? Transfer and Fragmentation yields (at the target) yield (Fragmentation) > 10 x yield (Transfer)

18. How to reach „heavy“ SHN? Pb, Bi targets actinide targets radioactive beams ► The N = 184 shell can be reached with exotic ion beams ► but: only small RIB intensities available: << 109 / s

19. Synthesis of Neutron-rich Isotopes with RIBs Predicted cross-sections in the region of expected shell closures example: AGe + 208Pb → A114* (G. Adamian, N. Antonenko, W. Scheid, DNS model) stable 282114 294114 expected yields for σ = 1 pb and ≤109 projectiles/s: 1 event in ≥30 years

20. The Fusion Process in Heavy Systems 10 - 100 mb Nuclear Molecule FUSION Compound Nucleus (CN) QUASI-FISSION (QF) FUSION-FISSION (FF) Fission Fragments Evaporation Residue (ER) σER = σcapture ∙ PCN ∙ Psurvival Superheavy systems: σER << σcapture→σcapture ≈ σQF + σFF = 10 – 100 mb

21. The Fusion Process in Heavy Systems Movement of the system on the potential energy surface V. Zagrebaev and W. Greiner ►Study of QF and FF as a function of beam energy and isospin allows the „mapping“ of the potential energy surface

22. Probing of the Z=120, N=184 Region The reaction ARb + 209Bi → A120* → N = 184 shell is reached with 95Rb beams Ecm / Bfu ~ ZCN2(exp. data) Ecm = Bfu but: Ecm / Bfu (1n channel) Z (compound nucleus) E*CN < Sn≈ 10 MeV → no neutron evaporation E*CN < Bf ≈ 5 MeV → no CN fission E*CN < 0 → no CN formation hindrance to fusion increases with Z → requires increasing beam energy

23. Future Experiments with Radioactive Ion Beams at HIE-ISOLDE (CERN) Decision of the CERN INTC, December 2012: „ ... ... “

24. The New Isotope 216U Observed decay chain and decay properties

25. The New Isotopes 223Am and 219Np Observed decay chain and decay properties