Fission and quasifission of composite systems with 
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: Transition from heavy-ion reactions involving S and Ca to Ti and Ni ions

Козулин, Э. М.; Knyazheva, G. N.; Novikov, K. V.; Itkis, I. M.; Иткис, М. Г.; Дмитриев, С. Н.; Oganessian, Yu. Ts.; Bogachev, A. A.; Kozulina, N. I.; Harca, I. M.; Trzaska, W. H.; Ghosh, T. K.

doi:10.1103/physrevc.94.054613

Cited by 57 publications

(57 citation statements)

References 46 publications

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“…The nature of these events can be investigated through their total kinetic energies (TKE), which are also obtained with the kinematic coincidence technique [7,8,45,46]. Figure 3 shows TKE as a function of M R for the three projectiles at E=V B ∼ 1.07 and θ c:m: > 135°.…”

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confidence: 99%

Mechanisms Suppressing Superheavy Element Yields in Cold Fusion Reactions

et al. 2019

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Superheavy elements are formed in fusion reactions which are hindered by fast nonequilibrium processes. To quantify these, mass-angle distributions and cross sections have been measured, at beam energies from below-barrier to 25% above, for the reactions of 48 Ca, 50 Ti, and 54 Cr with 208 Pb. Moving from 48 Ca to 54 Cr leads to a drastic fall in the symmetric fission yield, which is reflected in the measured massangle distribution by the presence of competing fast nonequilibrium deep inelastic and quasifission processes. These are responsible for reduction of the compound nucleus formation probablity P CN (as measured by the symmetric-peaked fission cross section), by a factor of 2.5 for 50 Ti and 15 for 54 Cr in comparison to 48 Ca. The energy dependence of P CN indicates that cold fusion reactions (involving 208 Pb) are not driven by a diffusion process.

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confidence: 99%

Mechanisms Suppressing Superheavy Element Yields in Cold Fusion Reactions

et al. 2019

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“…Experimentally, the measurement of fusion probability is required to distinguish quasifission between fusion-fission and fast fission [71][72][73][74][75][76]. The experimental characteristics of the quasifission process are different from the fusion-fission process [77].…”

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confidence: 99%

Fusion Dynamics of Low-Energy Heavy-Ion Collisions for Production of Superheavy Nuclei

Bao

2020

Front. Phys.

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One of the major motivations for low-energy heavy-ion collision is the synthesis of superheavy nuclei. Based on the following two main aspects, various theoretical and experimental studies have been performed to explore the fusion dynamical process of superheavy nuclei production. The first reason is to elucidate and analyze the synthesis mechanism of superheavy nuclei; the other is to search the favorable incident energy and the best combination of projectile and target to produce new superheavy elements and isotopes of superheavy elements.

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“…Maximum yields around A = 208 have been already observed and analysed [15,16,40] for QF experiments where only A was measured. They were interpreted either as arising from the N = 126 neutron shell closure [16] or, according to TDHF calculations that do predict accumulations of fragments with Z ≈ 82, from the proton shell closure [15]. The simultaneous A and Z measurement provides thus a clear evidence for a dominant effect of the closed shell at Z = 82 on the QF fragment yield.…”

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confidence: 92%

“…Due to these characteristics, the generic name quasi-fission (QF) is nowadays often used for all these mechanisms. Since the pioneering works, many experimental aspects of QF have been explored [8][9][10][11][12][13][14][15][16][17] and dynamical models, macroscopic or microscopic, have been developed in order to reproduce cross-sections, distributions of mass, angle, kinetic or excitation energy and some of the correlations between these observables [15,[18][19][20][21][22][23][24][25]. Considering the huge experimental difficulties to extract in a non-arbitrary way small cross-sections of fusion followed by fission from dominant quasi-fission cross-sections, a key issue for super-heavy nucleus formation studies, it is now essential to get a very good understanding of the QF mechanisms and to confront and improve the models with unambiguous exclusive data in order to reach reliable predictive capacities.A simultaneous determination of the fragment atomic number (Z) and mass (A) formed in QF or in fission processes remains nowadays a challenge [26][27][28][29][30], especially difficult because these quantities are most of the time measured after particle evaporation.…”

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Evidence for the Role of Proton Shell Closure in Quasifission Reactions from X-Ray Fluorescence of Mass-Identified Fragments

et al. 2017

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The atomic numbers and the masses of fragments formed in quasi-fission reactions have been simultaneously measured at scission in 48 Ti + 238 U reactions at a laboratory energy of 286 MeV. The atomic numbers were determined from measured characteristic fluorescence X-rays whereas the masses were obtained from the emission angles and times of flight of the two emerging fragments. For the first time, thanks to this full identification of the quasi-fission fragments on a broad angular range, the important role of the proton shell closure at Z = 82 is evidenced by the associated maximum production yield, a maximum predicted by time dependent Hartree-Fock calculations. This new experimental approach gives now access to precise studies of the time dependence of the N/Z (neutron over proton ratios of the fragments) evolution in quasi-fission reactions.PACS numbers: 25.70. Jj, 25.70.Gh, 32.50.+d, 24.10.Cn Since the mid-70s, it has been known that the formation of super-heavy nuclei by fusion is hindered by out-of-equilibrium mechanisms [1][2][3]. In these mechanisms, the available kinetic energy can be totally dissipated and large mass transfers between the projectile and the target can occur, leading to emerging fragments quite difficult to distinguish from fragments arising from fusion followed by fission (that might be mass symmetric or asymmetric) [4][5][6][7]. Due to these characteristics, the generic name quasi-fission (QF) is nowadays often used for all these mechanisms. Since the pioneering works, many experimental aspects of QF have been explored [8][9][10][11][12][13][14][15][16][17] and dynamical models, macroscopic or microscopic, have been developed in order to reproduce cross-sections, distributions of mass, angle, kinetic or excitation energy and some of the correlations between these observables [15,[18][19][20][21][22][23][24][25]. Considering the huge experimental difficulties to extract in a non-arbitrary way small cross-sections of fusion followed by fission from dominant quasi-fission cross-sections, a key issue for super-heavy nucleus formation studies, it is now essential to get a very good understanding of the QF mechanisms and to confront and improve the models with unambiguous exclusive data in order to reach reliable predictive capacities.A simultaneous determination of the fragment atomic number (Z) and mass (A) formed in QF or in fission processes remains nowadays a challenge [26][27][28][29][30], especially difficult because these quantities are most of the time measured after particle evaporation. In this letter, an experimental approach giving access for QF fragments to A and Z at scission will be presented and the data compared with predictions of a microscopic time dependent HatreeFock (TDHF) model [22]. The atomic number was determined from the coincident characteristic fluorescence X-rays, as already attempted for fission fragments [31], whereas the mass was determined from the velocities of the emerging fragments.A 48 Ti 19+ beam was accelerated at 5.75 MeV/nucleon by the Australi...

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Fission and quasifission of composite systems with Z=108−120 : Transition from heavy-ion reactions involving S and Ca to Ti and Ni ions

Cited by 57 publications

References 46 publications

Mechanisms Suppressing Superheavy Element Yields in Cold Fusion Reactions

Mechanisms Suppressing Superheavy Element Yields in Cold Fusion Reactions

Fusion Dynamics of Low-Energy Heavy-Ion Collisions for Production of Superheavy Nuclei

Evidence for the Role of Proton Shell Closure in Quasifission Reactions from X-Ray Fluorescence of Mass-Identified Fragments

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