The peculiarities of the production and decay of superheavy nuclei M.G.Itkis Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia

The dynamics of the fusion-fission of superheavy nuclei Experimental results. The peculiarities of the observables, the signatures of the Fusion-Fission/Quasi-Fission processes, multimodal fission phenomena The recent results on synthesis of superheavy nuclei The perspectives of the “hot” fusion reaction for the production of superheavy nuclei

Shape evolution in Fusion-Fission reactions Elastic scattering Coulomb excitation Quasi-elastic scattering Deep-inelastic scattering Incomplete pulse transfer Fast-fission Quasi-fission Fusion → CN → Fission Fusion → CN → de-excitation (n,  )→ ER In dependence on impact parameter and projectile energy :

Kinematics coincidence method. Double arm time-of-flight spectrometer CORSET

Experimental results The sharp change of the MED triangular shape for the reaction 48 Ca+ 208 Pb, where Fusion-Fission process dominates, to the Quasi-Fission shape of MED for the nuclei. The wide two-humped mass distribution with high peak of heavy fragment near double magic lead (M H  208) for the Quasi- Fission process. In spite of the dominating role of the Quasi-Fission process for these reactions we assume that in the symmetric region of the fragment masses (A/2  20) FF process coexists with QF. The Fusion-Fission mass distribution is asymmetric in shape with mass of the light fragment M L  amu ( see on the framings) Mass-energy distributions of the fission fragments of nuclei produced in “hot” fusion reactions with 48 Ca-projectiles E*  33 MeV

Mass Asymmetry in Low Energy Fission of Superheavy nuclei E*  MeV

Hot fusion reaction 48 Ca Cm  Fusion-Fission Dynamics M.G.Itkis, Yu.Ts.Oganessian, V.I.Zagrebaev, Phys.Rev.C65,2002, Total kinetic energy (MeV) Mass asymmetry (A 1 -A 2 )/(A 1 +A 2 ) Fragment mass number (u) Yield,%

Cold fusion reaction

Neutron and  -emission as probe FF/QF Neutron multi-detectors “DEMON” with trigger of fission fragments “CORSET” Two-dimensional matrixes TKE-Mass, Mass Yields, neutron multiplicities ( pre, post and tot ) for the reactions 48 Ca+ 208 Pb and 48 Ca+ 238 U

Total neutron multiplicities as function of atomic number of compound nuclei produced in the reaction with 26 Mg, 48 Ca and 58 Fe-projectiles Two-dimensional matrixes TKE-Mass, Mass Yields, neutron and  -multiplicities for the reaction with 48 Ca-projectiles on the targets 208 Pb, 238 U, 244 Pu, 248 Cm

Capture and Fusion-Fission Cross Sections The perspectives of the “hot” fusion reaction for the production of superheavy nuclei

Shell effects manifestation  QF /  cap (%)

. Fusion probability

σ xn = P xn ∙ Π (Γ n / Γ f ) I ~ (Γ n / Γ f ) x (Γ n / Γ f ) I ~ exp [(B f – B n ) / T] i=1 i=x where B f = B f LD + ΔE Shell 0 Survival probability the limit of the exp. sensitivity

Natural occurrence of Ca isotopes (in %): 40 Ca – Ca – Ca – Ca – Ca – Ca – x 400 → Ca 5+ isotope production high flux reactors (Oak Ridge, Dimitrovgrad ) isotope enrichment 98-99% S-2 separator (Sarov) technology of the target preparation – 0.3 mg/cm 2 Separation of super heavy nuclei and detection of their radioactive decays now: DGFRS

v ( A=48 ) = 0.11 c q = v ( A=288 ) = c q = 6.2+

Isotope charge (Z) and mass (A) identifications obtained by the measurements of neutron evaporation cross sections vs. excitation energy of compound nucleus

Decay Chains Observed in 243 Am + 48 Ca Reaction

odd-odd 

Synthesis of Element 118 in 249 Cf + 48 Ca Reaction Cm+ 48 Ca 242 Pu+ 48 Ca 238 U+ 48 Ca MeV 26.3 ms 0.68 s  2  SF(~90%) SF(~30%) MeV 970. MeV 7.87 s 0.28 s  4  9.5 MeV 8.53 MeV 0.3 s 2.80 min  6  9.30 MeV 1.84 h SF MeV 6.23 ms 0.55 s  2  1.0 ms SF SF(~60%) 10.5 MeV

Number of observed decays Z =

The formation of in the reactions with 48 Ca and 50 Ti-ions Mass-energy distributions of the fission fragments

Capture cross sections for the reactions 50 Ti+ 244 Pu and 48 Ca+ 246 Cm

N=174 N=182 N=184 N=184 Reactions of the production of elements with 58 Fe and 64 Ni-projectiles

10 8 y 10 5 y 1 y1 y 1 d1 d the search for SHE in Cosmic rays

Search in Nature Chemical properties (relativistic effect) Astrophysics (search for SHE in cosmic rays) Nucleosynthesis (test of the r-s process) Atomic physics (structure of SH-atoms) Elements with Z ≥ 120

Flerov Laboratory of Nuclear Reactions of JINR …in February Thanks for your attention