Mahmoud Yahia Ismail

Photon production cross sections in 12C-12C and 40Ca-40Ca collisions at Elab=84 and 200 MeV/A are calculated in the framework of the quantum molecular dynamics approach using the medium-dependent NN cross section obtained from the G matrix. Photons are assumed to be produced by incoherent pn bremsstrahlung and a simple classical expression for the production cross section is used. The effects of the equation of state for nuclear matter on the photon production cross section are studied in detail. In the 12C-12C collision, the authors found little difference in the photon cross section due to differences in the equation of state both at 84 and 200 MeV/A. In the 40Ca-40Ca collision, slightly more high-energy photons are produced in the case of the soft equation of state and the difference is slightly larger at higher incident energies.

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.

The authors have investigated proximity scaling for Pb+U and U+U potentials calculated recently from the collision of two infinite nuclear matters flowing through each other. They have found that the proximity theorem is satisfied to a good extent for the Pb+U system. for the U+U system a deviation between the proximity approach and the energy-density method has been found.

The authors investigate the proximity scaling for the nuclear part of the nucleus-nucleus potential derived from the collision of two infinite nuclear matters flowing through each other. It is found that the proximity theorem is satisfied to a good extent at each value of the projectile energy per nucleon. They simplify the interaction potential between different pairs of nuclei by the product of a geometrical factor, dependent on the radii of the interacting nuclei, and a gaussian distribution whose parameters depend on the projectile energy per nucleon.

The density matrix expansion method, together with three different effective nucleon-nucleon forces, is used to calculate the real part of the interaction potential between two 16O nuclei. The densities of the system are constructed using two different methods. In the first, a two-centre harmonic-oscillator potential is employed to construct the density and the kinetic energy density of the combined system and of the separated nuclei. In the second method, the density of the combined system is assumed to be the sum of the two separate densities and the kinetic energy densities are given approximately by the Thomas-Fermi approximation. The authors have found that the ion-ion potential derived using the second method shows a stronger energy dependence than that derived from the first. A comparison between the ion-ion potentials in the relevant tail region also showed that the second method includes, at zero energy, 30-60% of the exchange effects due to antisymmetrisation for the Negele force. At the same energy and for the Skyrme force the second method can be considered to be a very good approximation to the first.

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.

Nuclear reactions between two heavy interacting ions with nucleon transfer have been reconsidered. The direct nuclear reaction mechanism is considered. Different reaction processes are considered for single neutron or proton stripping and pickup reactions. The interacting nuclear potential of the transferred nucleon is taken to have the form of the Skyrme-type potential. With this representation for the nuclear potential of the transferred nucleon, an expression for the differential cross section is obtained by using the distorted-wave Born approximation. This expression is applied and considered for the heavy ion reactions with incident heavy ion projectiles B10, C13, O16, O18, and S32 bombarding the heavy targets Al27, Si28, Si29, Si30, and S32. The energies of the incident heavy ions have values in the range between 36.0 and 100.0 MeV. Numerical calculations of the differential cross sections are carried out. The theoretically calculated angular distributions are in good agreements with the experimental measurements. Reasonable spectroscopic factors are extracted from the present calculations. NUCLEAR REACTIONS Nucleon stripping and nucleon pickup induced by 36.0-100.0 MeV B10, C13, O16, O18, and S32 on Al27, Si28, Si29, Si30, and S32; calculated σ(θ). Finite range DWBA calculations, extracted spectroscopic factors. © 1983 The 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 energy density method was employed to calculate the real part of the 40Ca-40Ca interaction potential in the sudden approximation. A simple effective two-body force as well as the Skyrme and Negele interactions were used to derive the energy density functional. The real part of the 40Ca-40Ca potential calculated using Negele's (1970) force agrees well with the experimental results.

A simple semiphenomenological effective nucleon-nucleon interaction is used to show the effect of compressibility of nuclear matter on the real part of p plus Ca40 optical-model potential a proton energies up to 85 MeV. It is found that this nucleon-nucleon potential can predict both the depth and the shape of the phenomenological optical-model potential for energies up to 60 MeV assuming that is corresponds to a compression modulus of about 290 MeV.

This paper discusses the two different methods of interpreting Skyrme force, namely: the expansion of the two-body interaction and the density matrix expansion method. An approximation is presented which reduces the Hamiltonian energy density of the density matrix expansion to that produced by expanding the two-body force in Skyrme approximation.

The theory of nucleons elastically scattered from different nuclei is reconsidered. A nucleon-nucleon interaction of generalised Skyrme type is used to calculate the real part of the optical-model potential. This generalised force is used to introduce the consistency between the microscopic description of elastic scattering and the structure of bound nuclei. This theory is applied for neutron elastic scattering on 28Si, 32S, 40Ca and 208Pb at neutron energies of 11.0, 14.5, 20.0 and 26.0 MeV. Also, proton elastic scattering on the nuclei 40Ca, 58Ni and 208Pb is studied at proton energies of 21.3, 30.3 and 61.4 MeV. The imaginary parts of the optical-model potentials used in the present calculations are changed so that they produce the best fit to the experimental data. The calculated differential cross sections together with the polarisations are in good agreement with the experimental measurements.

A fourth-power momentum term is added to a simplified form of Skyrme interaction and the resulting two-body force is used to study the real part of the optical-model potential for the elastic scattering process n+ 40Ca at energies of 10 MeV and 50 MeV. It is found that the k 4 term affects the shape, the magnitude and the energy variation of the optical-model real well.

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.

A simple density-dependent effective nucleon-nucleon interaction is used to show the effect of compressibility of nuclear matter on the real part of the n+ 40Ca optical-model potential. It is found that the half-strength radius of the optical-model real potential decreases as the compression of nuclear matter increases.

The form factor of the two-nucleon stripping process **4**0Ca(t,p)**4**2Ca is studied using two types of effective interactions, namely the Skyrme and Brink-Boeker interactions. The results are compared with those of the ordinary zero-range potential. It is found that the effective interactions reduce the importance of the nuclear internal region. In addition the form factors calculated with effective interactions differ from the zero-range form factor in both the surface and asymptotic regions.