Mahmoud Yahia Ismail

n/a

The emission of Be, C, O, and Ne clusters from seven parent nuclei with neutron numbers around the neutron magicities N = 82 and 126 are considered. The universal decay law (UDL) formula, as well as the double-folding model derived from the Michigan three-range Yukawa–Paris NN interaction with zero- and finite-range exchange components, are utilized to compute the half-life time for 23 cluster decay processes. The calculations utilizing the UDL formula show satisfactory agreement with the experimental data. The reliable UDL formula is used to calculate log T c for more than 1500 cluster emitters and its variation with the neutron number, N d, of the daughter nuclei is presented. The behavior of log T c with neutron number variation is studied and correlated to the energy levels of the daughter nuclei. For a neutron number N d larger than the neutron magic number, log T c increases almost linearly with increasing N d, leaving the daughter nuclei in most cases with the same nuclear spin value. This linear behavior of log T c results from equal nuclear spin values of the daughter nuclei. At the magic neutron number, the nuclear spin changes strongly and as a result log T c increases as N d decreases. Log T c reaches to a maximum value when all the neutrons in the cluster are emitted from levels below the neutron gap. Leaving the daughter nuclei in the same spin produces almost linear variation of log T c. For protons in various clusters emitted from the same level or the same group of levels, log T c has almost the same value and the same behavior of variation with N d. Also, the values of log T c for specific types of cluster depend on the N to Z ratio for different isotopes of this cluster. From the available nuclear spin values, the neutron energy levels around the magic numbers are presented.

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.

We systematically investigated the behavior of the α-decay half-lives (Tα) for 20 isotopic chains of even–even nuclei, from 78Pt to 116Lv. Tα is calculated within the preformed cluster model. The α-core potential is determined by the double-folding model based on the M3Y-Reid nucleon–nucleon interaction. The Coulomb potential is also microscopically calculated by the folding procedure. To confirm our results, we used four different parameterizations of the involved proton and neutron densities, which are consistent with extensive microscopic calculations and electron scattering data. The results correlate the logTα behavior for the isotopes of an element with their proton energy levels. We found a clear similarity in the behavior of logTα with the number of neutrons of the daughter nuclei (Nd) for specific isotopic chains. The proton pairs forming the α-particles that emitted from the isotopes of the similar chains belong to the same proton energy level. We pointed out some neutron magic and semi-magic numbers corresponding to characteristic minima in the logTα variation with Nd. We interpreted these magic (semi-magic) numbers as the total number of neutrons filling the upper neutron level in the parent nucleus.

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.

The α-decay half-lives, Tα, for five heavy and nine superheavy even-even nuclei with 84 ≤ Z ≤ 92 and 116 ≤ Z ≤ 132, respectively, have been calculated within the density-dependent cluster model. The α-nucleus potential was derived by employing the double-folding model with a realistic NN interaction whose exchange part has a finite-range. We considered several isotopes for each Z-value. The behavior of log Tα against the neutron number variation for different isotopes of each element is investigated. We found a clear similarity in the behavior of log Tα for the isotopes of a number of successive elements. The proton pair in the emitted α particle, for these elements, comes from the same proton energy level. Also, the behavior of log Tα with the parent neutron number, for different isotopes of an element, was found to be governed by the existence of neutron magic number or neutron-level closure. The possibility to correlate the behavior of log Tα for several isotopes of a specific element with the proton and neutron energy levels of this element is investigated. Moreover, the behavior of log Tα when adding successive proton pairs to fill the energy level at different neutron numbers is studied. This work can be considered as a significant step forward to correlate the behavior of log Tα with the energy levels.

$$\alpha$$decay of 2000 parent heavy and superheavy nuclei, with atomic numbers in the range $$Z=80$$to $$Z=122$$, is considered. We calculated the half-life time, $$T_{\alpha}$$, of each nucleus using the density-dependent cluster model with M3Y-effective nucleon–nucleon interaction. The $$Q_{\alpha}$$values needed for calculation of $$T_{\alpha}$$were extracted from four different mass tables used frequently in $$\alpha$$-decay calculation. These tables are WS4, WS3, FRDM(2012), and DZ tables. The present study shows to what extent the behavior and value of $$T_{\alpha}$$, as the nucleon number varies, depends on choosing the mass table used to extract $$Q_{\alpha}$$values. For this purpose, we studied the variation of log $$T_{\alpha}$$and the corresponding $$1/Q_{\alpha}$$with the neutron number of the daughter nucleus, $$N_{d}$$, using the four different mass tables. The results show that the log $$T_{\alpha}$$variation follows the corresponding $$1/Q_{\alpha}$$variation. The two mass tables WS3 and WS4 predict almost the same log $$T_{\alpha}$$variation and agree in the magic and semi-magic numbers. For FRDM(2012) and DZ tables the variation of log $$T_{\alpha}$$with $$N_{d}$$follows the same $$1/Q_{\alpha}$$variation but the magic numbers deduced from these two tables do not agree with each other and almost differ from those predicted from WS3 and WS4. FRDM(2012) tables predict the main deep minimum at $$N_{d}=128$$instead of the magic neutron number $$N_{d}=126$$.

The α-decay half-lives of the superheavy nuclei (SHN) with Z = 119 and 120 are investigated by employing the density dependent cluster model. Within the double-folding model, the α-nucleus interaction potential is calculated microscopically using a realistic nucleon–nucleon (NN) interaction. The exchange part of the interaction potential is evaluated within a local density formalism, using the finite-range as well as the ordinary zero-range exchange components of the NN interaction. The influence of nuclear deformation is presented. The calculated values of α-decay half-lives for five isotopes of each of the SHN with Z = 119 and 120 have been compared with those values evaluated using other theoretical models. It was found that our theoretical values are in good agreement with their counterparts. The competition between α-decay and spontaneous fission is investigated and predictions for possible decay modes for the unknown nuclei 295−299119 and 298−302120 are presented. The probable cluster decay half-lives of 295119 and 298120 have been studied within the previously mentioned double-folding model as well as the unified formula (UF) of half-lives for α decay and cluster radioactivity, the scaling law by Horoi (Horoi) and the universal decay law (UDL). The cluster decay half-lives derived from the former three models are too large compared to α-decay half-lives, but the UDL formula predicts the possibility of heavy cluster emission. The mass number variations of the microscopic shell correction energy for different α-decay chains of Z = 119 and 120 isotopes are presented. The possible correlations between the shell effect and each of α-decay and cluster decay half-lives are discussed. We hope that the proposed theoretical predictions for α-decay chains and cluster radioactivity provide a new perspective to experimentalists.

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.