Diabatic shifts and fluctuations of heavy-ion fusion barriers

Berdichevsky, D. B.; Lukasiak, A.; Nörenberg, W.; Rozmej, P.

doi:10.1016/0375-9474(89)90548-4

Cited by 40 publications

(53 citation statements)

References 36 publications

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“…The reasons for this fusion hindrance are not understood. Various fusion hindrance models have been published lately [47][48][49][61][62], however, a complete dynamic theory including shell structure effects, both in the entrance and in the compound nuclear channel, is still missing. We can only make a 'semi-empirical' statement that the 'Pb road' using still heavier projectiles to go beyond element 109 [55] will require a large effort: raising, still, the beam intensities and the irradiation times as well as the detection efficiency (where possible) to reach a sensitivity for picobarn or even sub-picobarn cross sections.…”

Section: Resultsmentioning

confidence: 99%

How well do we understand the synthesis of heavy elements by heavy-ion induced fusion?

Reisdorf¹,

Schädel²

1992

Z. Physik A - Hadrons and Nuclei

171

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Experimental cross sections to synthesize heavy ion induced fusion reactions are confronted with calculations using the conventional picture of complete fusion after passing the barrier plus statistical deexcitation after complete equilibration. The sensitivity of the calculations to some of the parameters is demonstrated. Despite this sensitivity, a single parameter set is found that reproduces well the large body of data from experiments using actinide targets. By comparison, for the more symmetric entrance channels using targets around 2~we find a fusion hindrance that increases steeply with increasing compound nuclear charge. Predictions for a few reactions of future interest for the synthesis of heavy elements are also presented.

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Section: Resultsmentioning

confidence: 99%

How well do we understand the synthesis of heavy elements by heavy-ion induced fusion?

Reisdorf¹,

Schädel²

1992

Z. Physik A - Hadrons and Nuclei

171

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“…it explains the extra push energies. However, there exist individual deviations from the data which are related to nuclear structure effects [19], which are not included in the present version of the model. In the calculations we had to increase, as compared to the global parametrization [ld, 15], the radius of the folding potential by 10% (in agreement with the systematics of [17]) in order to obtain the correct onset of fusion and DIC.…”

Section: +L/dozw (T) (1)mentioning

confidence: 98%

A Langevin description of the competition between fusion and deep-inelastic collisions close to the barrier

Fröbrich

Marten

1991

Z. Physik A - Hadrons and Nuclei

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“…The validity of this diabatic model is critically dependent on the approach time to the barrier radius which must be short compared to the time needed to rearrange the nucleons adiabatically. Berdichevsky et al [ 11 ] estimate the latter time to be on the order of 2• 10 -2~ s, the approach time, i.e. the time to cover the distance of approximately 3 fm separating the interaction radius from the radius corresponding to the top of the potential barrier, being an order of magnitude shorter.…”

Section: N(g--n)mentioning

confidence: 98%

“…It is important to realize that the decision for fusion, in this model, occurs after the potential barrier has been passed [7,8,10]. A very different suggestion [11] is that the system behaves diabatically in the approach phase, leading to a fast dynamical rise of the fusion barrier. The latter is predicted to be strongly nuclear structure dependent.…”

Section: Introductionmentioning

confidence: 99%

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Competition between binary reactions and fusion in heavy-ion collisions at the Coulomb barrier

Reisdorf¹,

Kratz

Bellwied

et al. 1992

Z. Physik A - Hadrons and Nuclei

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Mass and charge distributions for binary reaction channels have been measured for the reactions 86Kr with 76Ge, I~ and 13~ at the Coulomb barrier using chemical separations and 7-ray spectroscopy. These systems span the region where dynamical hindrance to complete fusion sets in. The binary reactions can be subdivided into two components associated with i) reflection from the outer potential barrier (quasielastic), and ii) reseparation after passing the barrier (complex reactions). The sum of complex-reaction channels and evaporation residues from complete fusion can be reproduced by a barrier passing calculation. The fraction of the barrier passing flux leading to reseparation increases from 26 +_ 10% for the lightest system to more than 90% for the heaviest system. The data indicate that fusion hindrance is primarily caused by reseparation shortly after passage of the barrier before Swiatecki's conditional saddlepoint is overcome, resulting in partitions close to the entrance channel configuration. In addition, for the heaviest system, a quasifission component representing somewhat less than 20% of the barrier-passing flux was observed. From the missing masses of fragment pairs we can deduce that the reseparating complex-reaction products have kinetic energies well below the fusion barrier and share the excitation energy in a way similar to the sawtooth-like curve known from low-energy fission. The quasielastic, predominantly one-and two-nucleon transfer channels, have strongly varying cross sections for the three systems despite similar effective Q-values. A systematics of one-neutron transfer cross sections at the Coulomb barrier is established and shown to differ considerably from the smooth behaviour observed at energies 20-30% above the barri- er. The connection to nuclear polarization phenomena and orbit matching is pointed out.

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Diabatic shifts and fluctuations of heavy-ion fusion barriers

Cited by 40 publications

References 36 publications

How well do we understand the synthesis of heavy elements by heavy-ion induced fusion?

How well do we understand the synthesis of heavy elements by heavy-ion induced fusion?

A Langevin description of the competition between fusion and deep-inelastic collisions close to the barrier

Competition between binary reactions and fusion in heavy-ion collisions at the Coulomb barrier

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