Fusion hindrance for a positive<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Q</mml:mi></mml:mrow></mml:math>-value system

Jiang, C. L.; Back, B. B.; Esbensen, H.; Greene, J. P.; Janssens, R. V. F.; Henderson, D.J.; Lee, Hye Young; Lister, C. J.; Notani, M.; Pardo, R. C.; Patel, N.; Rehm, K. E.; Seweryniak, D.; Shumard, B.; Wang, X.; Zhu, S.; Mișicu, Ş.; Collon, P.; Tang, Xiaodong

doi:10.1103/physrevc.78.017601

Cited by 53 publications

(38 citation statements)

References 28 publications

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“…This has been observed for 58 Ni + 58 Ni, 90 Zr + 92 Zr and 60 Ni + 89 Y, and more recently similar results have been obtained for several other systems [312][313][314][315][316]. Before we discuss the physics involved in this phenomenon, one should understand clearly what one means by hindrance.…”

Section: Hindrance Of Fusion At Deep Sub-barrier Energiessupporting

confidence: 64%

Recent developments in fusion and direct reactions with weakly bound nuclei

et al. 2015

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Section: Hindrance Of Fusion At Deep Sub-barrier Energiessupporting

confidence: 64%

Recent developments in fusion and direct reactions with weakly bound nuclei

et al. 2015

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“…If the cross section could be approximated by the Wong's formula, this quantity would converge to a constant value as the energy decreases well below the Coulomb barrier. The hindrance of the fusion cross section at deep sub-barrier energies was first observed for the 58 Ni + 58 Ni system [20,21] (see figure 5) but similar results have been reported for several other systems [22][23][24][25][26][27]. It should be stressed Further details are given in Ref.…”

Section: Fusion At Deep Sub-barrier Energiessupporting

confidence: 49%

Reaction mechanisms in heavy ion fusion

Canto

Gomes

Lubián

et al. 2011

EPJ Web of Conferences

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Abstract. We discuss the reaction mechanisms involved in heavy ion fusion. We begin with collisions of tightly bound systems, considering three energy regimes: energies above the Coulomb barrier, energies just below the barrier and deep sub-barrier energies. We show that channel coupling effects may influence the fusion process at above-barrier energies, increasing or reducing the cross section predicted by single barrier penetration model. Below the Coulomb barrier, it enhances the cross section, and this effect increases with the system's size. It is argued that this behavior can be traced back to the increasing importance of Coulomb coupling with the charge of the collision partners. The sharp drop of the fusion cross section observed at deep sub-barrier energies is addressed and the theoretical approaches to this phenomenon are discussed. We then consider the reaction mechanisms involved in fusion reactions of weakly bound systems, paying particular attention to the calculations of complete and incomplete fusion available in the literature.

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“…3 of Ref. [2]). Therefore, a fusion experiment has been recently carried out at the Laboratori Nazionali di Legnaro (LNL) with the purpose to extend the data of 30 Si + 30 Si down to energies deeply below the Coulomb barrier.…”

Section: Introductionmentioning

confidence: 88%

“…Indeed, 28 Si is strongly deformed with an oblate shape while 30 Si is nearly spherical. In that work the fusion of the asymmetric system 28 Si + 30 Si [1,2] was explained by considering one-neutron and successive two-neutron transfer channels in the coupling scheme. The case of 28 Si + 28 Si involving deformed nuclei shows an unusual behavior, where the cross section is hindered [3] just below the barrier and then enhanced at lower energies, as shown in the comparison with the coupled-channels (CC) calculations.…”

Section: Introductionmentioning

confidence: 99%

Isotopic effects in sub-barrier fusion of Si + Si systems

et al. 2018

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Background: Recent measurements of fusion cross sections for the 28 Si + 28 Si system revealed a rather unsystematic behavior; i.e., they drop faster near the barrier than at lower energies. This was tentatively attributed to the large oblate deformation of 28 Si because coupled-channels (CC) calculations largely underestimate the 28 Si + 28 Si cross sections at low energies, unless a weak imaginary potential is applied, probably simulating the deformation. 30 Si has no permanent deformation and its low-energy excitations are of a vibrational nature. Previous measurements of this system reached only 4 mb, which is not sufficient to obtain information on effects that should show up at lower energies. Purpose: The aim of the present experiment was twofold: (i) to clarify the underlying fusion dynamics by measuring the symmetric case 30 Si + 30 Si in an energy range from around the Coulomb barrier to deep sub-barrier energies, and (ii) to compare the results with the behavior of 28 Si + 28 Si involving two deformed nuclei. Methods:30 Si beams from the XTU tandem accelerator of the Laboratori Nazionali di Legnaro of the Istituto Nazionale di Fisica Nucleare were used, bombarding thin metallic 30 Si targets (50 μg/cm 2 ) enriched to 99.64% in mass 30. An electrostatic beam deflector allowed the detection of fusion evaporation residues (ERs) at very forward angles, and angular distributions of ERs were measured. Results: The excitation function of 30 Si + 30 Si was measured down to the level of a few microbarns. It has a regular shape, at variance with the unusual trend of 28 Si + 28 Si. The extracted logarithmic derivative does not reach the L CS limit at low energies, so that no maximum of the S factor shows up. CC calculations were performed including the low-lying 2 + and 3 − excitations. Conclusions: Using a Woods-Saxon potential the experimental cross sections at low energies are overpredicted, and this is a clear sign of hindrance, while the calculations performed with a M3Y + repulsion potential nicely fit the data at low energies, without the need of an imaginary potential. The comparison with the results for 28 Si + 28 Si strengthens the explanation of the oblate shape of 28 Si being the reason for the irregular behavior of that system.

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Fusion hindrance for a positiveQ-value system

Cited by 53 publications

References 28 publications

Recent developments in fusion and direct reactions with weakly bound nuclei

Recent developments in fusion and direct reactions with weakly bound nuclei

Reaction mechanisms in heavy ion fusion

Isotopic effects in sub-barrier fusion of Si + Si systems

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