Mahmoud Yahia Ismail

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The empirical Royer formulas were readjusted with new set of coefficients using the latest experimental data and the recent evaluated -decay half-lives over a wide range of 573 nuclei between 52 Z 118. The effects of the orbital angular momentum, isospin asymmetry, and parity have been examined in improving the adopted formulas. The modified formulas were tested for their accuracy by comparing with the recent experimental data and other theoretical calculations. The prediction of -decay half-lives of several isotopes of the superheavy nuclei with which have not yet been experimentally synthesized, are presented and compared with other theoretical approaches. The behavior of in relation to the neutron number variation is explored for about 40 isotopes of each element. Based on the minima found in variation with neutron number, we found neutron stability at 190, 196, 200, 202, 204, 210, 216, 218, 220 and 228. The behavior of with neutron variation for heavy and superheavy nuclei is almost the same as that found using more heavy and complicated calculations. The present method can be applied easily to study large number of nuclei.

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.

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.

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 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.

The study show the effect of the local density and the accuracy of neglecting s-dependence on direct part of α-α interaction potential. The large error in neglecting s-dependence produced at (R<2 fm) for BDM3Y3 -Ried force. In the surface and tail region (R≥3) the error is less than 50%.

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 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 study show the effect of the local density and the accuracy of neglecting s-dependence on the exchange part of α-α interaction potential. This effect is bout 30% for the force BDM3Y2-Ried while it is less than 7% for BDM3Y1 -Reid. For BDM3Y3 force which corresponds to large value of compressibility coefficient, the corresponding error is too large at separation distance R=0.

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.

The Coulomb and nuclear heavy ion (HI) potentials are derived for an interacting pair of deformed nuclei assuming sharp surface model for each nucleus. The orientation and separation dependences of the Coulomb and nuclear interactions are studied. It is assumed 238U + 238U as an example, and the effect of quadrupole term is investigated. For the nuclear potential part based on M3Y nucleonnucleon interaction, the sharp surface model shows much difference compared with the more accurate frequently used multipole expansion method while the success of this model in calculating the Coulomb potential between this deformed pair of nuclei exists in the physically important surface region. © 2010 World Scientific Publishing Company.