Effects of diabaticity on fusion of heavy nuclei in the dinuclear model ...

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Y Z Y A 0,12 0,10 0,08 0,06 0,04 0,02 0,00 0 10 20 30 40 50 0,12 0,10 0,08 0,06 0,04 0,02 Z 0,00 0 20 40 60 80 100 120 140 A 7-3: The same as in Fig. 7-2 for the fusion reaction Figure 48 + Ca 208 Pb→256 (solid line) 102 for the cold fusion reactions and 50 Ti+ 208 Pb→ 258 (dashed line), 104 64 + Ni 208 Pb→ 272 110 (dotted line) and 76 Ge + 208 Pb→ 284 114 (dashed-dotted line). 101
elements from Z=104 to Z=112 in the cold fusion reactions, the experimentalists observed a rapid fall-<strong>of</strong>f <strong>of</strong> the evaporation residue cross sections (about four orders <strong>of</strong> magnitude) with increasing charge number <strong>of</strong> the compound nucleus [7, 8]. In the model <strong>of</strong> fusion based on the DNS-concept, the fusion cross sections and excitation functions for the cold fusion reactions leading to the formation <strong>of</strong> superheavy elements are obtained in good agreement with the experimental data [20]. The structure <strong>of</strong> the mass (charge) distribution <strong>of</strong> the quasi-fission products well corresponds to the peculiarities <strong>of</strong> the driving potential (the DNS potential energy as a function <strong>of</strong> mass (charge) asymmetry) shown in chapter 4. In order to illustrate the connection between the quasi-fission product yield and the driving potential, Fig. 7-4 shows the quasi-fission charge distribution for the reactions 110 Pd+ 136 Xe (η=0.1), 86 Kr+ 160 Gd (η=0.3) and 76 Ge+ 170 Er (η=0.4), which lead to the formation <strong>of</strong> the same compound nucleus 246 Fm. The distributions reveal large widths and one can observe a notable drift in charge (mass) away from the initial charge (mass) asymmetry <strong>of</strong> the interacting nuclei. The product masses are substantially different from the target—projectile masses. It is seen that the symmetric fragments can be formed in the quasi-fission process if the entrance DNS is an asymmetric one. We can observe that the main peak <strong>of</strong> the distributions is around the initial configuration <strong>of</strong> the DNS. Compar- ing Fig. 7-4 with Fig. 4-7a), we observe that there is a correlation between the peaks <strong>of</strong> the quasi-fission distribution and the minima <strong>of</strong> the driving potential. The inner fusion barrier Bη increases with decreasing mass asymmetry η (Figs. 4-1to 4-7b)), while the quasi-fission barrier B qf becomes smaller because the Coulomb repulsion increases with decreasing η and leads to very shallow pockets in the nucleus-nucleus potential for nearly symmetric configurations. Therefore, the decay <strong>of</strong> the initial DNS dominates in symmetric or nearly symmetric collisions. The experimental fusion probability becomes larger with the increase <strong>of</strong> the mass asymmetry η in the entrance channel [118]. This experimental evidence for a hindrance <strong>of</strong> fusion has been mainly concluded from the impossibility to produce fermium evaporation residues with nearly symmetric projectile-target combinations [118]. The main conclusions are: 1) The quasi-fission products <strong>of</strong> fusion reactions are correctly described within the DNS model: diffusion in charge (mass) asymmetry and in relative distance (the DNS decay) coordinates contributes to the yield <strong>of</strong> quasi-fission products. 2) The quasi- 102
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Effects of
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1 Introduction 6 1.1 The DNS-concep
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Chapter 1 The elements existing in
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observed the rapid fall-of<
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Figure 1-1 illustrates the compound
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smaller than the extra-extra push e
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fusion and quasi-fission processes
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In the present chapter we have pres
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higher collective velocities to rep
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2.1 General considerations We want
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couplings. Diabatic basis states ψ
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Chapter 3 The synthesis of<
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is calculated within the TCSM using
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E adiab (MeV) n E diab (MeV) n 30 2
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E diab (MeV) n 60 55 50 45 40 100Mo
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3-5: Diabatic potentials for the sy
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3-7: The same as in Fig. 3-6 for th
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The estimated collective velocities
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3-10: Diabatic contributions as a f
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effects give a justification for th
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The similarity of
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4.1.3 Alternative microscopical met
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to the DNS concept [18, 34], cross
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U (MeV) 28 27 26 25 24 23 22 21 20
Page 49 and 50: U (MeV) 35 30 25 20 15 10 90Zr + 12
Page 51 and 52: 4-1: Fusion barriers B Table TCSM
Page 53 and 54: U (MeV) 40 30 20 10 20 10 0 a) b) 9
Page 55 and 56: experimental separation energy allo
Page 57 and 58: means a neglect of
Page 59 and 60: the case of an ind
Page 61 and 62: single particle density matrix exte
Page 63 and 64: following ratio in the limit <stron
Page 65 and 66: 5-1: Dependence of
Page 67 and 68: the microscopical mass parameter <s
Page 69 and 70: 5-3: Mass parameter Mεε as a func
Page 71 and 72: 5-4: Mass parameter Mεε as a func
Page 73 and 74: the approximate expressions (Eqs. (
Page 75 and 76: (10 3 m fm 2) M , M λλ εε 25 20
Page 77 and 78: (10 3 m fm 2) M εε M (10 λλ 4 m
Page 79 and 80: ~ f k (MeV -1) 0,20 0,15 0,10 0,05
Page 81 and 82: V (MeV) 30 25 20 15 10 5 0 -5 -10 1
Page 83 and 84: to the dependence of</stron
Page 85 and 86: where the lifetime t 0 of</
Page 87 and 88: 6-2: a) Time-dependent dynamical po
Page 89 and 90: Table 6-1: Quasi-fission and inner
Page 91 and 92: 6-3: Time-dependent average width <
Page 93 and 94: Chapter 7 In the quasi-fission proc
Page 95 and 96: The value of t0 is
Page 97 and 98: Y Z Y A 0,10 0,08 0,06 0,04 0,02 0,
Page 99: estimated from the difference betwe
Page 103 and 104: fission process is an important fac
Page 105 and 106: the neck coordinate ε and
Page 107 and 108: • The time-dependent transition b
Page 109 and 110: Appendix A For describing nucleus-n
Page 111 and 112: where The volume is V0 = 1 2 m0ϖ 2
Page 113 and 114: ϕ nz(z) = ⎧ ⎪⎨ ⎪⎩ C−1
Page 115 and 116: Appendix B The collective response
Page 117 and 118: [1] S.G.Nilsson et al., Phys. Lett.
Page 119 and 120: [27] N.V.Antonenko et al., in 1 st
Page 121 and 122: [63] Yu.F.Smirnov and Yu.M.Tchuvil
Page 123 and 124: [97] H. Hofmann et
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Effects of diabaticity on fusion of heavy nuclei in the dinuclear model ...

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