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Systematics of fusion probability in reactions leading to super-heavy nuclei Ning Wang ( ) Guangxi Normal University www.imqmd.com 2011 Dec., Beijing.

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Presentation on theme: "Systematics of fusion probability in reactions leading to super-heavy nuclei Ning Wang ( ) Guangxi Normal University www.imqmd.com 2011 Dec., Beijing."— Presentation transcript:

1 Systematics of fusion probability in reactions leading to super-heavy nuclei Ning Wang ( ) Guangxi Normal University Dec., Beijing

2 N. Wang Introduction Calcualtions of capture cross sections Survival probablity W sur Fusion probabilty P CN

3 N. Wang new superheavy elements 48 new isotopes Yu. Oganessian T 1/2 = 320d 249 Bk + 48 Ca 117 Yu. Oganessian SHE in JINR 109-th Session of the SC of JINR, Feb , 2011, Dubna ???

4 N. Wang S.Hofmann, GSI , 7477hours / 312days, 2 events Theoretical support for these very time-consuming and extremely-expensive experimentsis vital in choosing the optimum target-projectile-energy combinations, and for the estimation of cross sections. 50 Ti, 54 Cr, 58 Fe, 64 Ni, 70 Zn Pb 48Ca 1 20 Cf 1 10

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6 I. Capture II. Decay III. Formation # Coulomb barrier # Barrier distribution (~ ) # Deformation & dynamics … (~ present) # Fission barrier # Masses & shell corrections (~ present) # Mass distributions … # Quasi-fission barrier # Potential energy surface (~ …) # Dynamics …

7 N. Wang I. Capture cross sections with the Skyrme energy-density functional Density distributions of the reaction partners Entrance-channel fusion barrier Fusion cross sections Skyrme energy-density functional Barrier penetration & empirical fusion barrier distribution D(B) M. Liu, N. Wang, Z. Li, X. Wu and E. Zhao, Nucl. Phys. A 768 (2006) 80 Ning Wang, et al., Phys. Rev. C 74 (2006)

8 N. Wang KineticNuclearCoulomb Skyrme energy-density functional M. Brack, C. Guet, H.-B. Hakanson, Phys. Rep. 123, 275 (1985). Skyrme force SkM*

9 N. Wang Spherical symmetric Fermi functions Search for the minimum of energy by varying densities (R 0p, R 0n, a p, a n ) according to Hohenburg-Kohn theorem 1. Determination of density distributions

10 N. Wang E1E1 E2E2 Sudden approximation for density R V.Yu. Denisov and W. Noerenberg, Eur. Phys. J. A15, 375 (2002). 2. Entrance-channel fusion barrier

11 N. Wang with Determination of D(B) is the key of this approach D(B) to empirically take into account the coupling between the relative motion and other degrees of freedom such as deformation etc. 3. Fusion (capture) cross section Min Liu, Ning Wang, et al., Nucl. Phys. A 768 (2006) 80

12 N. Wang for reactions with nuclei near the beta-stability line but the neutron-shell is not closed

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14 Deviations from experimental data for 120 reactions About 70% systems are less than 0.005, which gives the system error 18%. N. Wang et al., J. Phys. G: 34 (2007) 1935 rms

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17 The fusion excitation functions of a series of reactions with 16 O bombarding on medium mass targets.

18 N. Wang Large-angle quasi-elastic scattering PRC 78, (2008)

19 N. Wang S. G. Zhou Tail of barrier distribution influences the large-angle quasi-elastic cross sections

20 N. Wang II. Survival probability W sur with HIVAP The sensitive parameters: 1. fission barriers (Liquid-drop barriers, Sierks barriers…) 2. level density parameters (Fermi gas model, angular-momentum and shape-dependent) 3. masses shell corrections and particle separation energies

21 N. Wang 1). Fission barrier Nuclei Cohen-Swiatecki Sierk Dahlinger MWS 244 Pu No

22 N. Wang Obtained deviations with different models for 51 fusion-fission reactions N. Wang, M. Liu and Y. Yang, Sci. China G 52, 1554 (2009)

23 N. Wang 2). Level density parameters In the standard HIVAP code: E d =18.5MeV, r a =1.153fm

24 N. Wang Radius parameter r a in the level density parameter

25 N. Wang Optimal value of the radius parameter r a 68% reactions have a value smaller than , Estimated systematic errors of the HIVAP code: 1.85W sur and W sur /1.85

26 N. Wang A reliable nuclear mass model is needed for studies on synthesis of super-heavy, nuclear astrophysics and nuclear symmetry energy, etc. Mass Olympics Trento 2008 WS : PRC 81 (2010) WS*: PRC 82 (2010) WS3: PRC 84 (2011) WS* 3). Masses of super-heavy nuclei

27 N. Wang Ning Wang, et al., Phys. Rev. C 77 (2008) Fusion-fission EDF HIVAP

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34 M. Itkis Dubna 1) Driving potential 2) Quasi-fission 3) Calculations of evaporation residual cross sections III. Fusion probability P CN (preliminary)

35 N. Wang Y. Oganessian, 109th Session of the JINR Scientific Council, 2010, Dubna. 2) quasi-fission barrier B qf E sh

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37 Mean barrier height 3) Evaporation residual cross sections

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39 Uncertainty at E>B m : 1.18 (capture) x 1.85 (W sur ) x 2 (P CN ) = 4.4

40 N. Wang Collected by Junlong Tian

41 N. Wang A. K. Nasirov, et al., Phys. Rev. C 84, (2011)

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43 Results from Nan Wang ( )

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45 Zagrebaev, et al., arXiv: v1 For 4n channel

46 N. Wang Opt. 50 Ti+ 249 Bk 50 Ti+ 249 Cf 54 Cr+ 248 Cm 58 Fe+ 244 Pu Nasirov (2009) (2011) ~ 100 fb ~ 10 pb ~ 70 fb ~ 6 fb Liu & Bao (2011) ~ 600 fb ~ 100 fb Nan Wang (2011) ~1000 fb ~ 200 fb ~ 40 fb~ 30 fb Zagrebaev (2008) ~ 50 fb ~ 40 fb ~ 20 fb~ 5 fb This work (2011) ~ 35 fb ~ 20 fb ~ 5 fb~ 3 fb

47 N. Wang Conclusion and discussion Methods for calculations of capture cross sections, survival probability of compound nucleus and the fusion probability in fusion reactions leading to super-heavy nuclei are established step by step. Coulomb barrier, fission barrier and quasi-fission barrier play important role for the calculations of three parts. More precise calculations for masses, fission barrier and the study on dynamics of fusion and fission processes are still required.

48 N. Wang China Institute of Atomic energy Zhu-Xia Li Xi-Zhen Wu Kai Zhao ( ) ( ) ( ) Institute of Theoretical Physics (CAS) En-Guang Zhao Justus-Liebig-Univ. Giessen Werner Scheid Guangxi Normal Univ. Min Liu Anyang Normal Univ. Jun-Long Tian

49 N. Wang Thanks for your attention I am very grateful to Prof. Shan-Gui Zhou ( ) for many discussions and valuable suggestions This work was supported by Alexander von Humboldt Foundation and National Natural Science Foundation of China


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