1. Lecture 4 1.The role of orientation angles of the colliding nuclei relative to the beam energy in fusion-fission and quasifission reactions. 2.The effect of quasifission products on the angular distribution anisotropy of the fissionlike products. 3. The angular momentum distribution of different reaction products

2. 2

3. 3 Dependence of the capture and fusion cross sections on the orientation angle of the axial symmetry axis of reactants

4. 4 Nucleus-nucleus potential as a function of the distance between nuclei and orientation their axial symmetry axis

5. 5 Comparison of the capture and fusion excitation functions with the experimental data and Langevin calculations S. Mitsuoka, et al. PRC 62 (2000) 054603. Y. Aritomo, M. Ohta, Nucl.Phys. A744 (2004) 3

6. 6 Partial fusion cross section as a function of the orientation of axial symmetry axis reactants Nasirov A.K. et al. The role of orientation of nuclei symmetry axis in fusion dynamics, Nucl. Phys. A 759 (2005) 342

7. 7 Dependence of the driving potential (а) and quasifission barrier (b) on the mutual orientations of the axial symmetry axes of nuclei

8. Dependence of competition between complete fusion and quasifission on energy and orbital angular momentum ? !

9. 9 A.K. Nasirov et al., Eur. Phys. Jour. A34, 325-339 (2007)

10. Averaged effective moment of inertia of dinuclear system. 10

11. 11

12. Cross sections, anisotropy, and averaged angular momentum square ℓ 2 for two reactions 19 F+ 208 Pb and 16 O+ 238 U 12 A.K. Nasirov et al., Eur. Phys. Jour. A34, 325-339 (2007)

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14. 14 Experiment Theory

15. Angular anisotropy of the fusion-fission and quasifission fragments 15 A.K. Nasirov et al., Eur. Phys. Jour. A34, 325-339 (2007)

16. What we know about quasifission fragments? The mass distribution its fragments has a maximum usually near magic numbers Z=20, 28, 50, 82 and N=20, 28, 50, 82; Total kinetic energy distribution is very close to Viola systematics as for fusion-fission: TKE=Z 1 Z 2 e 2 /D(A 1,A 2 ); Angular distribution of fragments has more large anisotropy in comparison with that of fusion-fission. angular distribution of quasifission fragments is mainly anisotropic but it may be isotropic and angular distributionof fusion-fission fragments may be isotropic in dependence on the reaction dynamics. We would like to stress that angular distribution of quasifission fragments is mainly anisotropic but it may be isotropic and angular distribution of fusion-fission fragments may be isotropic in dependence on the reaction dynamics.

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19. 19 Competition between fusion-fission and quasifission processes in the 32S + 184W reaction H. Zhang et al. Phys. Rev. C81 034611 (2010)

20. The angular distribution of the fission products is described in the framework of the standard statistical model (SSM) usually making use of the fact that the fission saddle point configuration can be treated as a transition state between the compound system in its quasi-equilibrium state and the two separated fission fragments through saddle point. Consequently, in such case, the SSM may not properly describe the angular anisotropy of pure fission fragments in reactions with massive nuclei.

22. Variance of the projection of J on fission axis

23. Capture, quasifission, fusion and fast-fission cross sections

24. Anisotropy A=1+ /4K 0 2

25. Interpretation of the experimental data presented as fusion-fission data in the 32 S+ 184 W reaction

26. 26 Angular momentum distribution of compound nuclei formed in collisions with different orientations of the target 154 Sm at different values of the beam energy. G. Fazio et al. Jour. Phys. Soc. of Japan., Vol. 77, No. 12, No. 12, December, 2008, 124201

27. 27 Calculation of decay of dinuclear system

28. 28 Collective enhancement of level density of DNS

29. Effect of the entrance channel on the formation and characteristics of reaction products

30. Where we should look for quasifission fragments?

31. 31 Mass-angle distribution of the binary products in full momentum transfer (capture) reactions: 16 O+ 204 Pb (a), 34 S+ 186 W (b) and 48 Ti+ 170 Er (c,d). ( c ) M R =M 2 /(M 1 +M 2 ) E lab= 208.0 MeV E lab= 245.0 MeV E lab= 188.9 MeV E lab= 126.0 MeV Dependence of the mass –angle distribution on the initial beam energy for the 48 Ti+ 170 Er reaction (c,d): at small energy angular distribution of quasifission fragments becomes more isotropic. That is reason why quasifission seemed to be disappear for 48 Ca+ 154 Sm reaction in the experiments discussed in Knyazheva et al. Phys. Rev.C 75, 064602 (2007). Our interpretation was presented in A.K.N. et al. Phys.Rev. C 79 024606 (2009). ( d )

32. Interpretation of the experimental data presented as fusion-fission data in the 32 S+ 184 W reaction

33. 33 The role of the entrance channel and shell structure of reactants at formation of the evaporation residues in reactions leading to the same compound nucleus 216 Th: a) Capture b) Complete fusion c) Evaporation residues cross sections.

34. 34 Driving potential U driving ( c ) for reactions 40 Ar+ 172 Hf, 86 Kr+ 130 Xe, 124 Sn+ 92 Zr leading to formation of compound nucleus 216 Th : U driving =B 1 +B 2 -B (1+2) +V( R ) Due to peculiarities of shell structure B fus (Kr) > Bfus (Kr) and, consequently,  fus (Kr+Xe) <  fus (Zr+Sn)

35. 35 Angular momentum distribution for the complete fusion σ fus (L) (E lab ) as a function of momentum and and beam energy for reactions leading to formation of 216 Th. G. Fazio, et al., Journal of the Physical Society of Japan 388, 2509 (2003).

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37. The role of mass asymmetry and angular momentum in formation of evaporation residues 37

38. 38

39. Evaporation residue (ER) cross sections and gamma multiplicity distributions have been measured for 16 O + 184 W and 19 F + 181 Ta systems in the excitation energy range of 50–90 MeV, leading to the same compound nucleus 200 Pb ∗. Comparison of experimental results of both the systems shows that ER cross sections and moments of gamma multiplicity distribution of 16 O + 184 W system are significantly higher than those of 19 F + 181 Ta system at higher excitation energies. Present measurements directly shows the experimental signature of entrance channel effect even with the systems which are not very different with respect to their entrance channel mass asymmetry. It is further demonstrated that the reduction in the ER cross section and moments of spin distribution for 19 F + 181 Ta system is mainly due to the suppression of fusion of higher ℓ values. 39

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41. Angular momentum distribution for dinuclear system (quasifission) and compound nucleus (fusion-fission and Evaporation residues) 41

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43. Calculation of the physical quantities characterizing multinucleon transfer reactions

44. Calculation of the excitation energy of nucleus where H P, λ P and N P are Hamiltonian, chemical potential and number nucleons, respectively, for the projectile-like nuclei.

45. Calculation of the excitation energy of nucleus

47. Total kinetic energy loss So, our model allows us to calculate excitation energy of the interacting nuclei as a sum of the excitation energy of their proton and neutron subsystems. This is important in case of calculation of the pre-equilibrium emission of protons or neutrons at more high energies relative to the Coulomb barrier of the entrance channel.

48. Comparison of the calculated results for mean values of the charge and mass numbers in 56 Fe+ 165 Ho and 74 Ge+ 165 Ho reactions.

49. Comparison of the ratio of the light fragment excitation energy to the total excitation energy of reaction products.

50. Conclusions The complete fusion mechanism in the heavy ion collisions strongly depends on the entrance channel peculiarities: mass (charge) asymmetry, shell structure of interacting nuclei, beam energy and angular momentum (impact parameter of collision). The hindrance to formation of the compound nucleus is mainly caused by quasifission and fast-fission processes which are in competition with complete fusion. Mass and angular distributions of the fusion-fission, quasifission and fast-fission processes may overlap making difficulties at analysis experimental data. Quasifission takes place at all values orbital angular momentum. The experiments by registration of binary fragments of reactions in coincidence with neutrons, charged particles and gamma-quanta allow to reconstruct true reaction mechanism. 50