Mahmoud Yahia Ismail

The role of neutron transfer is investigated in the fusion process near and below the Coulomb barrier within the empirical channel coupling approach. The possibility of neutron transfer with positive Q-values considerably increases the barrier penetrability. The enhancement of fusion cross sections for 58Ni+ 64Ni, 32S+ 64Ni, 40Ca+ 48Ca, and 40Ca+ 124Sn is well reproduced at subbarrier energies by the empirical channel coupling approach including the coupling to the neutron-transfer channels. The predictions of the fusion cross sections for several combinations of colliding nuclei are also proposed which may shed additional light on the effect of neutron transfer in fusion processes. A huge enhancement of deep subbarrier fusion probability was found for light neutron-rich weakly bound nuclei. This may be quite important for astrophysical primordial and supernova nucleosynthesis. © 2012 Elsevier B.V..

The energy dependence of the ion-ion reaction cross section has been investigated using the eikonal approximation to study the effects of the Pauli blocking and surface contribution to the optical potential. This leads to theoretical cross sections lower than the data. If the collective surface contribution is added to the volume part, one obtains reasonable agreement with experiment at higher energies.

We study the role of the projectile breakup in the fusion process by example of the 6Li reactions with the 59Co, 144Sm and 209Bi targets in vicinity of the Coulomb barrier. The coupled channel and distorted wave approaches are employed in order to calculate the complete fusion and the breakup cross sections, respectively. The partial cross sections in both the channels are compared in order to estimate the breakup fraction responsible for the suppression of complete fusion. The calculations are compared with available experimental data. The conclusions and recommendations are made.

The real and imaginary parts of the optical model potential for several pairs of magic nuclei have been calculated by a double folding procedure. The complex effective interaction is calculated from the Reid soft core potential by solving the Bethe-Goldstone equation in two colliding nuclear matters. The calculated potentials were approximated with a Woods-Saxon shape. We studied the dependence of the parameters of these Woods-Saxon forms on the masses of the interacting nuclei. © 1984 Springer-Verlag.

The sensitivity of cluster-decay half-life time to the isospin effect of the nucleon–nucleon ( NN )interaction and the neutron-skin thickness is explored in the framework of the
Wentzel–Kramers–Brillouin approximation. Within the generalized double-folding model, the
cluster-daughter potential is calculated in terms of the isoscalar and isovector parts using the
explicit proton and neutron density distributions. Realistic density-dependent Michigan-three-Yukawa
(CDM3Y1 and CDM3Y6) NN interactions with the finite-range exchange NN force are considered in the
present work. The calculated cluster-decay half-lives including the isospin effect and the
differences between neutron and proton density distributions are found to be in somewhat better
agreement with the experimental data as compared without these effects. This may indicate the
necessity of considering the isospin effect and the neutron–proton differences of the density
distributions in cluster-decay, especially for extremely neutron-rich nuclei. Predictions of cluster
decay half-lives from possible cluster emitters are presented which may be helpful for future
experiments. The present study could be a significant step forward in improving the description of
cluster decay half-lives.

The structure of some even-even superheavy nuclei with the proton number Z = 98-120 is studied using a semi-microscopic but not self-consistent model. The macroscopic energy part is obtained from the Skyrme nucleon-nucleon interaction in the semi-classical extended Thomas-Fermi approach. A simple but accurate method is derived for calculating the direct part of the Coulomb energy. The microscopic shell plus pairing energy corrections are calculated from the traditional Strutinsky method. Within this semi-microscopic approach, the total energy curves with the quadrupole deformation of the studied superheavy nuclei were calculated. The same approach features the well known 208Pb or 238U nuclei. For each nucleus the model predictions for the binding energy, the deformation parameters, the half-density radii and comparison with other theoretical models are made. The calculated binding energies are in good agreement with the available experimental data. © 2010 Pleiades Publishing, Ltd.

A new averaging process of the calculation of α-decay half-lives for heavy and superheavy nuclei is studied in the framework of a deformed density-dependent cluster model. The potential between a spherical α particle and a deformed daughter nucleus is calculated numerically from the double-folding model by the multipole expansion method. The nuclear potential is calculated at each α-particle emission angle applying the Bohr-Sommerfeld condition at each case. The penetration factors and the half-lives for all the emission angles are evaluated with the new averaging process and compared with older values based on a fixed value of the nuclear potential depth. Finally, the half-lives of 83 even-even heavy nuclei in the atomic-number range 82-118 are calculated by the two methods and compared with their experimental values and the corresponding half-lives of the spherical daughter nuclei. © 2012 American Physical Society.

The energy dependence of the real part of the ion-ion interaction potential is studied using an energy density functional derived from the Negele realistic nucleon-nucleon interaction. It is found that the Negele force produces an ion-ion potential which varies slowly with energy compared to that derived using a simple two-body effective interaction. NUCLEAR REACTIONS Antisymmetrization effects, Fermi gas model, momentum density, Negele force, energy dependence of ion-ion potential. © 1982 The American Physical Society.

The interactions of 48Ca spherical nucleus are considered with the deformed targets 224Ra and 244Pu to form the super heavy elements 272Hs and 292114 (292Fl), respectively. The double folding model with effective density dependent M3Y-NN force, and the energy density functional method based on Skyrme force are used to derive the nucleus–nucleus interaction. The effect of deformation and orientation on the Coulomb barrier parameters is studied, and the results are compared with the corresponding quantities derived from a simple model based on the proximity approach for the nuclear part and simple analytical formula for the Coulomb interaction. Consistent behavior of the results is obtained at certain ranges for deformation parameters and orientations.

Improved NRDX empirical formula for $$\alpha $$- and cluster decay half-lives is modified by adding the effects of angular momentum, isospin asymmetry and parity. The coefficients are determined using the latest experimental data for $$\alpha $$-decay half-lives of 573 nuclei and the available 22 cluster decay half-lives. The modified formulas produced the $$\alpha $$- and cluster decay half-lives and agree with calculations of other similar formulas. We used the new formulas to calculate the half-lives of cluster emissions of the SHN with $$Z=120$$, 122, 124, and 126, which have not yet been experimentally synthesized.

The interaction potential for a deformed-spherical pair is calculated, and the error in using the truncated multipole expansion is evaluated for different numbers of terms of the expansion considered. It was found for the internal region of the nuclear part that three terms are sufficient, but for the surface and tail region up to five terms are necessary, while for the Coulomb potential three terms were found to be sufficient.

In nuclear theory, there is always a quest for possible extensions of the nuclear landscape and extending our knowledge to the limits of nuclear existence. In this study, we examine the stability and structural properties of a wide range of nuclei in super- and ultra-heavy region in a phenomenological semi-microscopic approach. we calculated the shell correlation energy, residual pairing correction energy, two-nucleon separation energy and two-nucleon energy gap for 3670 even?even nuclei along ?-stability line and two-neutron driplines in the ranges 70 ≤ Z ≤ 274 with 80 ≤ N ≤ 548 and 70 ≤ Z ≤ 212 with 126 ≤ N ≤ 548, respectively. To assure reliability and confidence of the new results in the ultra-heavy region, we extended the search space to include heavy and super-heavy nuclei. We report 83 double magic nuclei and address the predominance of proton and neutron magic numbers. Our calculations reproduced known results on nuclear magicity and present strong evidences on islands of stability and magic numbers in super- and ultra-heavy regions. We also address shifts in nuclear magicity along the nuclear landscape close to the ?-stability line and close to the neutron rich regions.In nuclear theory, there is always a quest for possible extensions of the nuclear landscape and extending our knowledge to the limits of nuclear existence. In this study, we examine the stability and structural properties of a wide range of nuclei in super- and ultra-heavy region in a phenomenological semi-microscopic approach. we calculated the shell correlation energy, residual pairing correction energy, two-nucleon separation energy and two-nucleon energy gap for 3670 even?even nuclei along ?-stability line and two-neutron driplines in the ranges 70 ≤ Z ≤ 274 with 80 ≤ N ≤ 548 and 70 ≤ Z ≤ 212 with 126 ≤ N ≤ 548, respectively. To assure reliability and confidence of the new results in the ultra-heavy region, we extended the search space to include heavy and super-heavy nuclei. We report 83 double magic nuclei and address the predominance of proton and neutron magic numbers. Our calculations reproduced known results on nuclear magicity and present strong evidences on islands of stability and magic numbers in super- and ultra-heavy regions. We also address shifts in nuclear magicity along the nuclear landscape close to the ?-stability line and close to the neutron rich regions.

A method is presented to calculate the exact HI Coulomb potential between spherical and deformed nuclei in the framework of the double folding model. We used realistic density distributions taking the deformations of the target into account. We have compared between our calculations and one of the more recent analytical expressions based on assuming sharp surface of the interacting nuclei. We have found that the finite surface diffuseness affects strongly the HI Coulomb interaction in the inner region and has a smaller effect in the tail region. Moreover, neglecting non-linear higher order terms in the analytical expressions produces errors in the outer region of the Coulomb interaction. © 2003 Published by Elsevier Science B.V.

A method is described to calculate the heavy ion reaction cross section σ R when one of the two nuclei is deformed. This method is based on both the double folding model and the optical limit approximation to Glauber theory. Both finite range of the nucleon-nucleon (NN) interaction and in-medium effects of NN cross section are included. The interacting pair 12C -238U is taken to study orientation, energy, and deformation dependence of σ R. The finite range force increases the value of σ R by about 5%. In-medium NN cross section decreases σ R by about 1.9% compared to the free NN cross section.

The interaction potential for a deformed-spherical pair of nuclei is calculated using the folding model derived from different range nucleon-nucleon (NN) interactions. Five spherical projectiles of different mass numbers scattered on the 238U deformed target are considered. The error in the heavy ion (HI) potential by using the truncated multipole density expansion is evaluated for each case. We find systematic trends of the percentage error in the HI potential depending on the number of multipoles considered; this percentage decreases if the mass number of the projectile or the range of the NN force increases, and it becomes smaller for small values of the separation distance between two nuclei or when higher deformation parameters vanish. The maximum error in using the truncated density expansion is estimated in the case of two deformed interacting nuclei. © 2008 IOP Publishing Ltd.

The form factors for the two-nucleon transfer reaction are studied, in zero-range DWBA, using five different types of Skyrme nucleon-nucleon potential. The results are compared with those using an interaction potential between two free nucleons. The results are independent of the incident triton energy, the state of the residual nucleus and the method used to calculate the form factor.