CCDEF - A simplified coupled-channel code for fusion cross sections including static nuclear deformations

Fernandez-Niello, J.; Dasso, C.H.; Landowne, S.

doi:10.1016/0010-4655(89)90100-8

Cited by 182 publications

(42 citation statements)

References 2 publications

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“…The systematic and statistical errors in the spectra are smaller than the size of the data points in the figure. The solid line in the figure corresponds to the coupled channel prediction (CCDEF) [15]. In the present calculation, we have used axially symmetric shape of the target, characterized by nuclear quadruple and hexadecapole deformation parameters β 2 = 0.217 and β 4 = 0.09 [16].…”

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confidence: 99%

Direct evidence of “washing out” of nuclear shell effects

et al. 2015

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Constraining excitation energy at which nuclear shell effect washes out has important implications on the production of super heavy elements and many other fields of nuclear physics research. We report the fission fragment mass distribution in alpha induced reaction on an actinide target for wide excitation range in close energy interval and show direct evidence that nuclear shell effect washes out at excitation energy ∼ 40 MeV. Calculation shows that second peak of the fission barrier also vanishes around similar excitation energy. One of the major areas that have generated unprecedented interest among contemporary nuclear physicists and chemists is the synthesis of super heavy elements (SHE). It is known from the Liquid Drop Model (LDM) of the nucleus [1] that if the two fundamental nuclear parameters, the attractive nuclear surface potential and the repulsive coulomb forces are taken into account, then our nuclear chart may end at around element number 104. This is simply because, nuclei with Z ≥ 104 immediately fission as there is no barrier to prevent their decay. However, elements have been synthesized beyond that atomic number [2].The observed stability of these heavy elements is believed to originate from the microscopic shell effects in nuclei. While LDM predicts the bulk properties of nuclei and explains their collective behavior, nuclear Shell Model [3] explains these shell gaps and the single-particle nature of nuclear states. Both the bulk properties and the shell properties of nuclei can be incorporated by adding a shell-correction term to the liquid-drop model energy. Strutinsky [4,5] considered the shell effect as a deviation from uniform liquid drop model prediction and used the shell averaged single particle energy as a correction term to the liquid drop model energy. The liquid drop barrier height diminishes smoothly with the increase in atomic number as the nuclear fissility increases. However, as the shell correction term retains the fluctuations in the shell model energy, it is found that the incorporation of this shell correction alters the fission barrier and in fact, causes to develop large barrier to decay that can increase alpha or fission half-lives by several orders of magnitude for the heavy elements. Thus shell effects play a central role in determining the stability of the super heavy elements. Many important nuclear phenomena such as the fission isomers [6], super deformed nuclei [7] and new magic numbers in the exotic nuclei [8] are the consequences of the shell effect. * tilak@vecc.gov.in It is generally believed that shell effects are washed out at higher excitation energy [9]. For the production of the super heavy elements by heavy ion bombardment on actinides targets, the compound nuclei are always formed with an excitation energy exceeding a few tens of MeV. Judicious choice of the excitation energy is critical as the production cross section of the SHE may be increased by a few orders of magnitude if the beam energy is increased by few MeV. Therefore, constraining the exci...

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confidence: 99%

Direct evidence of “washing out” of nuclear shell effects

et al. 2015

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“…where ) ( In the isocentrifugal approximation [2,5,6], where the angular momentum of the relative motion in each channel is replaced with the total angular momentum J (in the literature, this approximation is also referred to as the rotating frame approximation or the no-Coriolis approximation), the coupledchannels equations derived from the Hamiltonian (1) read …”

Section: Coupled-channels Formalism For Heavy-ion Fusion Reactionsmentioning

confidence: 99%

“…Coupled-channels calculations as well as experimental data shows that the effect of nuclear intrinsic degrees of freedom can be analyzed in more detail through the so-called fusion barrier distributions [3,1] which is defined as the second derivative of the product between the center of mass energy, E and the fusion cross section, both simplified [4,5] and realistic [6,7], coupledchannels codes have been used. In the codes, phenomenological Woods-Saxon potential has been assumed for the nuclear part of the potential.…”

Section: Introduction *mentioning

confidence: 99%

Coupled–Channels Analyses For Heavy–Ion Fusion Reactions of 16O+92Zr,144,148Sm Systems

Zamrun

Hagino

2010

Atom Indo.

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We study in detail the fusion reaction of 16 O with 92 Zr and 144,148 Sm at sub-barrier energies with coupled-channels framework using the error function potential for the nuclear potential. In particular, we investigate the effects of multiphonon excitations in target nuclei on experimental fusion cross section and barrier distributions for these reactions. We show that the present coupled-channels calculations well account for the experimental data of the fusion cross section as well as the fusion barrier distributions. It is shown that the coupled-channels calculations taking into account the coupling up to double quadrupole phonon excitations in 92 Zr well reproduce the experimental fusion cross section as well as fusion barrier distribution for 16 O+ 92 Zr. However, for 16 O+ 144 Sm, coupling to single quadrupole and octupole phonon states in 144 Sm can well explain the experimental data. And the coupling up to triple quadrupole phonon states and double octupole phonon excitations in 148 Sm are needed in order to reproduce the experimental data. Our study indicates the error function potential is adequate for analyses of the heavy-ion fusion reactions.

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“…A new version of the program (CCDEF) has been implemented recently to treat static deformations in nuclei such as 154 Sm, 232 Th, and 236 U. 33 Coupling to transfer channels has not been included in any of the calculations presented in this work. The nuclear potential used in the code has a Wood-Saxon shape with parameters as given by Ref.…”

Section: Model Calculationsmentioning

confidence: 99%