Journal : Pramana – Journal of Physics
Publisher: springer
ISI journal with impaact factor 0.64

Nuclear Structure of the 26Mg Nucleus Using Microscopic Theory

khalid S.Jassim Raad A. Radhi

1Department of Physics, College of Education for pure Science, University of Babylon, PO Box 4, Hilla-Babylon, IRAQ
2Department of Physics, College of Science, University of Baghdad, Baghdad, IRAQ
khalidsj@uobabylon.edu.iq




The shell-model assumption says that we can separate the system into a core part and a valence part, and describe the interaction between the core and the valence particle, and that among the valence particles. The interaction between them will excite the core. This process, known as core excitation, will then give rise to an effective force between the valence particles since two of them will have shifted their state as a consequence of their interaction with the core, while the core has returned to the original state. This process can be described as a polarization of the core by one of the valence particles. The core polarization effect on the form factor is based on a microscopic theory, which combines shell-model wave functions and configurations with higher energy as first order perturbations; these are called "core-polarization effects". The scattering of electrons from the nucleon and from nuclei at high energies has provided important information about the size of the nucleus. The electron energies are in the region of 100 MeV and higher, so that the de Broglie wave length associated with the electron is in the range of the nuclear forces. At these energies the electron acts as a probe for measuring the size of the nucleus which, if not a point, is expected to be of dimension of the order of a few Fermis [1]. The universal sd-shell interaction (USD) Hamiltonian [2] has provided realistic sd-shell (0d5/2, 0d3/2,1s1/2) wave functions for use in nuclear structure models, nuclear spectroscopy and nuclear astrophysics for over two decades. It is also an important part of the Hamiltonian used for the p-sd [3] and sd-pf [4-6] model spaces [7]. The USD Hamiltonian is based on 63 two-body matrix elements (TBME) and three single-particle energies (SPE) given in Table I of ref [8]. The USDA (universal sd-shell interaction A) and The USDB (universal sd-shell interaction B) interactions [7] are a new USD-type Hamiltonian based on 66 parameters to fit 608 energy data in sd-shell nuclei (A=16-40) with a root mean square (rms) deviation of 130 KeV and 170 KeV, respectively [7, 9]. These new interactions have clearly resolved the fluorine problem as well as all of the oxygen isotopes. The single-particle energies for the 0d3/2, 0d5/2 and 1s1/2 orbitals are (in MeV) -1.9798, -3.9436, and -3.0612 for the USDA interaction and -2.1117, -3.9257 and -3.2079 for the USDB interaction. Richter and Brown [9] have made a comparison between the experimental and theoretical results of corresponding levels in the 26Mg levels based on energies and electron scattering form factor. Results based on the new sd-shell interactions USDA and USDB. The enlarge model space (1p3/2, 1p1/2, 2s1/2 and 1d3/2) have been [10] used to calculate the electron scattering form factors for some p-shell nuclei. The results improve the agreement data remarkably well and provide an essential role for electromagnetic transitions and electron scattering form factors.
Shell model calculation have been used to calculated electron scattering form factors [11] for different states in 10B, 32Sc and 48Ca nuclei. The results with CP effects inclusion modify the form factors markedly and describe the experimental values very well in the range of the momentum transverse (q) values dependence. The form factor calculations using shell model code NuShell take into account the collective modes in nuclei, the CP effects is evaluated by adopting the purely empirical Tassie Model [12] together with the calculated ground state charge density distribution obtained for the low mass 1s-0d shell nuclei using the occupation