The fusion–fission and quasi-fission processes in the reaction 48Ca + 208Pb at energies near the Coulomb barrier

Прохорова, Е. В.; Bogachev, A. A.; Иткис, М. Г.; Itkis, I. M.; Knyazheva, G. N.; Kondratiev, N. A.; Козулин, Э. М.; Крупа, Л.; Oganessian, Yu. Ts.; Pokrovsky, I. V.; Pashkevich, V. V.; Rusanov, A. Ya.

doi:10.1016/j.nuclphysa.2008.01.016

Cited by 67 publications

(56 citation statements)

References 63 publications

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“…Namely, the averaged value of P fus ≈18% can be derived with the macroscopic fission barriers obtained in the SM analysis of the xn excitation functions measured for the C+Cm reactions. This value is significantly lower than the P fus values extracted from the fission data [56] and obtained with the theory [57] but is much higher than it follows from the DNS model calculation [58], as shown in Figure 7. The P fus values obtained in the present analysis of 'cold' fusion reactions slightly differ from those estimated earlier in the preliminary study [51].…”

Section: -P8contrasting

confidence: 54%

“…Using these macroscopic fission barriers for the analysis of the ER and fission cross sections obtained in the 48 Ca+ 208 Pb reaction (see [55] and [56], respectively, and Refs therein), one can come to the similar result as obtained for 40 Ar+ 208 Pb. Namely, the averaged value of P fus ≈18% can be derived with the macroscopic fission barriers obtained in the SM analysis of the xn excitation functions measured for the C+Cm reactions.…”

Section: -P8mentioning

confidence: 59%

“…Solid line corresponds to the averaged P fus value for 40 Ar+ 208 Pb and 48 Ca+ 208 Pb, whereas a dashed line in the left panel corresponds to the calculation fitted to the measured 50 Ti+ 198 Pt ER cross sections. P fus values extracted from fission experiments [53,56] and obtained with theoretical models [57,58] are also shown. See the text for details.…”

Section: -P8mentioning

confidence: 99%

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Fusion probability and survivability in estimates of heaviest nuclei production

Sagaidak

2012

EPJ Web of Conferences

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Abstract. Production of the heavy and heaviest nuclei (from Po to the region of superheavy elements close to Z=114 and N=184) in fusion-evaporation reactions induced by heavy ions has been considered in a systematic way within the framework of the barrier-passing model coupled with the statistical model (SM) of de-excitation of a compound nucleus (CN). Excitation functions for fission and evaporation residues (ER) measured in very asymmetric combinations can be described rather well. One can scale and fix macroscopic (liquid-drop) fission barriers for nuclei involved in the calculation of survivability with SM. In less asymmetric combinations, effects of fusion suppression caused by quasi-fission (QF) are starting to appear in the entrance channel of reactions. QF effects could be semi-empirically taken into account using fusion probabilities deduced as the ratio of measured ER cross sections to the ones obtained in the assumption of absence of the fusion suppression in corresponding reactions. SM parameters (fission barriers) obtained at the analysis of a very asymmetric combination leading to the production of (nearly) the same CN should be used for this evaluation.

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Section: -P8contrasting

confidence: 54%

Section: -P8mentioning

confidence: 59%

Section: -P8mentioning

confidence: 99%

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Fusion probability and survivability in estimates of heaviest nuclei production

Sagaidak

2012

EPJ Web of Conferences

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“…In sub-barrier reactions with closed-shell nuclei, it has been shown [14] that increasing the "magicity" in the entrance channel results in narrower mass distributions, correlated with a reduced mass-angle correlation, indicative of longer sticking times. Indeed, for the 48 Ca+ 208 Pb reaction, measured mass distributions [20] appear consistent with a fusion-fission mechanism. These results led to the conclusion that "magicity" plays its strongest role when the N/Z values of the projectile and target nuclei are matched.…”

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confidence: 61%

“…To define the smooth trends in quasifission, a large number of MAD measurements have been selected, for beam energies somewhat above the capture barrier (typically by ∼ 6%). Here the known effects of deformation alignment [10,11,17,19] and shell structure observed in measurements at below-barrier energies [14,20] are much reduced [11,21,22]. However the beam energies should not be too far above the capture barriers, otherwise high angular momenta would be introduced in the collisions, which would then not be representative of heavy element formation reactions.…”

Section: Introductionmentioning

confidence: 99%

Systematic study of quasifission characteristics and timescales in heavy element formation reactions

Hinde

Williams

Mohanto

et al. 2016

EPJ Web of Conferences

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Superheavy elements can only be created in the laboratory by the fusion of two massive nuclei. Mass-angle distributions give the most direct information on the characteristics and time scales of quasifission, the major competitor to fusion in these reactions. The systematics of 42 mass-angle distributions provide information on the global characteristics of quasifission. Deviations from the systematics reveal the major role played by the nuclear structure of the two colliding nuclei in determining the reaction outcome, and in hindering or favouring heavy element production.To form very heavy and superheavy elements (SHE), heavy-ion fusion reactions are used. Their cross sections can be significantly suppressed [1] by quasifission [2]. This dynamical non-equilibrium process results when the combined system formed after capture separates into two (fission-like) fragments in times ∼10 −20 s, before a compact compound nucleus is formed. The probability of quasifission (P QF ) can be very large, with the corresponding probability of compound nucleus formation (P CN = 1 -P QF ) being lower than 10 −3 in unfavourable cases. Understanding the competition between quasifission and fusion is thus very important in predicting the best fusion reactions to use to form new isotopes of heavy and super-heavy elements.A key quantity characterizing quasifission is its "sticking time" between capture of the two nuclei inside the entrance channel potential barrier [4] and breakup (scission). Quasifission mass-angle distributions (MAD) first measured at GSI in the 1980s [2,5] showed that quasifission timescales could often be shorter than the rotation time of ∼10 −20 s. However, subsequently only a few measurements [6,7] were made until recent years, when an extensive series of experiments (using the Australian National University Heavy Ion Accelerator Facility and CUBE spectrometer) were carried out [3,[8][9][10][11][12][13][14][15][16]. The kinematic coincidence technique used in the measurements [2,3,17] provides direct information on the mass-ratio of the fragments at scission; thus, the data are represented in terms of mass ratio M R , rather than pre-or According to the characteristics of the MAD (minimum mass yield at symmetry, mass-angle correlation with peak yield at symmetry, and no significant mass-angle correlation), they are assigned as type MAD1, MAD2 and MAD3 respectively [3]. There is a clear correlation between the MAD class and the entrance channel charge product. Other entrance channel characteristics are important in determining the sticking times and MAD characteristics, including neutron richness [14,18], and shell structure including static deformation [11] and magic numbers [14].To improve our quantitative understanding of the role of shell structure in the dynamics of quasifission, we make an analogy with the liquid drop model approach to nuclear masses, in which localized shell effects can be quantified when the underlying smooth (liquid drop) trends are well defined. To define the smooth trends in ...

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Parametrisation of the experimental fusion–fission cross-sections

Manjunatha

Sowmya

2018

Pramana - J Phys

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The fusion–fission and quasi-fission processes in the reaction 48Ca + 208Pb at energies near the Coulomb barrier

Cited by 67 publications

References 63 publications

Fusion probability and survivability in estimates of heaviest nuclei production

Fusion probability and survivability in estimates of heaviest nuclei production

Systematic study of quasifission characteristics and timescales in heavy element formation reactions

Parametrisation of the experimental fusion–fission cross-sections

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