Tidal Effects and the Proximity Decay of Nuclei

McIntosh, A. B.; Hudan, S.; Metelko, C.; Souza, R. T. de; Charity, R. J.; Sobotka, L. G.; Lynch, W. G.; Tsang, M. B.

doi:10.1103/physrevlett.99.132701

Cited by 16 publications

(33 citation statements)

References 20 publications

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“…It may be that the present structure model for 8 Be is not good enough, or that the Coulomb field of the target changes the structure of 8 Be, possibly causing it to be stabilised. A similar phenomenon has been hinted at in 8 Be emission following heavy-ion collisions [29].…”

Section: Discussion and Outlooksupporting

confidence: 75%

Classical dynamical modelling of near-barrier breakup

et al. 2017

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Abstract. The complete fusion of light, weakly-bound nuclides is known to be significantly suppressed with respect to comparable well-bound projectiles or with respect to single barrier penetration model calculations. Strong α-clustering in these light systems mean that they very easily disintegrate into clusters, either via direct excitation of their intrinsic cluster continuum, or via transfer reactions which connect to unbound states in neighbouring nuclides. This breakup is thought to reduce the probability for complete fusion. Here we discuss which processes cause breakup, whether or not breakup happens fast enough, and the interpretation of measurements made at the Australian National University of breakup using classical dynamical models. Understanding the intimate details of breakup, and the resonances through which it proceeds, will be crucial in determining its likely influence on fusion.

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Section: Discussion and Outlooksupporting

confidence: 75%

Classical dynamical modelling of near-barrier breakup

et al. 2017

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“…Independent of expectations based on the known mean lives of resonant states, deduced from their widths, it is possible to experimentally separate breakup close to the target nucleus from breakup (asymptotically) far away by examining the energy and angular correlations of the resulting fragments [17,21]. When breakup occurs asymptotically, which is also associated with a well defined excitation energy E x of the projectile-like nucleus, the laboratory opening angle between the two fragments, θ 12 , and the orientation of the relative momentum of the breakup fragments, β, in their centre of mass frame are related.…”

Section: A Distinguishing Near-target and Asymptotic Breakupmentioning

confidence: 99%

Importance of lifetime effects in breakup and suppression of complete fusion in reactions of weakly bound nuclei

et al. 2016

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Background: Complete fusion cross sections in collisions of light, weakly bound nuclei and high Z targets show suppression of complete fusion at above-barrier energies. This has been interpreted as resulting from breakup of the weakly bound nucleus prior to reaching the fusion barrier, reducing the probability of complete charge capture. Below-barrier studies of reactions of 9 Be have found that breakup of 8 Be formed by neutron stripping dominates over direct breakup, and that transfer triggered breakup may account for the observed suppression of complete fusion.Purpose: This paper investigates how the above conclusions are affected by lifetimes of the resonant states that are populated prior to breakup. If the mean life of a populated resonance (above the breakup threshold) is much longer than the fusion timescale, then its breakup (decay) cannot suppress complete fusion. For shortlived resonances, the situation is more complex. This work explicitly includes the mean life of the short-lived 2 + resonance in 8 Be in classical dynamical model calculations to determine its effect on energy and angular correlations of the breakup fragments and on model predictions of suppression of cross sections for complete fusion at above-barrier energies.Method: Previously performed coincidence measurements of breakup fragments produced in reactions of 9 Be with 144 Sm, 168 Er, 186 W, 196 Pt, 208 Pb and 209 Bi at energies below the barrier have been re-analysed using an improved efficiency determination of the BALiN detector array. Predictions of breakup observables and of complete and incomplete fusion at energies above the fusion barrier are then made using the classical dynamical simulation code PLATYPUS, modified to include the effect of lifetimes of resonant states.Results: The agreement of the breakup observables is much improved when lifetime effects are included explicitly. Sensitivity to sub-zeptosecond lifetime is observed. The predicted suppression of complete fusion due to breakup is nearly independent of Z, and has an average value of ∼ 9%. This is below the experimentally determined fusion suppression which is typically ∼ 30% in these systems.Conclusions: Inclusion of resonance lifetimes is essential to correctly reproduce breakup observables. This results in a larger fraction of nuclei remaining intact at the fusion barrier radius, compared with calculations that do not explicitly include lifetime effects. The more realistic treatment of breakup followed in this work leads to the conclusion that the suppression of complete fusion cannot be fully explained by breakup prior to reaching the fusion barrier. Only one third of the observed fusion suppression can be attributed to the competing process of breakup. Other mechanisms that can suppress complete fusion must therefore be investigated. One of the possible candidates in cluster transfer that produces the same heavy target-like nuclei as those formed by incomplete fusion. PACS numbers: 25.40.Hs,25.70.Hi,25.70.Pq,25.70.Ef It was recognised early on [11] that ver...

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“…In principle, it cannot be predicted unless one models the breakup process in the short distance domain and then follows the evolution to asymptotic distances. Although it has been customary to assume that the asymptotic relative energy is equal to the difference between the excitation energy of the resonant state and the breakup Q value [23,31,32], corrections to this value due to the Coulomb post acceleration of the light breakup products in the field of a heavier partner have been observed and/or calculated under particular model assumptions [15,33]. According to the calculations presented in Ref.…”

Section: B Relative Energiesmentioning

confidence: 99%

Differential and total cross sections of noncapture breakup reactions in the6Li+144Sm system

et al. 2014

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The breakup of the projectile-like fragments in reactions induced by 6 Li beams on a 144 Sm target at energies close to the Coulomb barrier has been measured through the coincident detection of the emitted light particles. The emphasis of the measurements and the data analysis were placed in the complete characterization of the α-deuteron breakup mode by means of the identification of the breakup fragments and the determination of the total Q value, relative energy of the breakup products, and the angular distribution of their emission. Within the ranges of these variables covered by the present measurements, the results for the 6 Li→d+α mode show a clear dominance of the resonant channel through the 3 + state at 2.186 MeV over other resonant and nonresonant channels. Differential cross sections as a function of the center-of-mass angles of the intermediate binary collision and of the breakup emission, as well as integrated cross sections as a function of energy, have been obtained. The data are compared with those measured for competing processes in the same system and with the results of calculations based on a dynamic classical model that describes noncapture breakup, incomplete fusion, and complete fusion.

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Tidal Effects and the Proximity Decay of Nuclei

Cited by 16 publications

References 20 publications

Classical dynamical modelling of near-barrier breakup

Classical dynamical modelling of near-barrier breakup

Importance of lifetime effects in breakup and suppression of complete fusion in reactions of weakly bound nuclei

Differential and total cross sections of noncapture breakup reactions in the6Li+144Sm system

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