NUCLEAR PHYSICS CORE POLARIZATION EFFECTS OF SOME ODD SD-SHELL NUCLEI USING M3Y EFFECTIVE NUCLEON-NUCLEON INTERACTION KHALID S. JASSIM 1,2 and HASSAN ABU KASSIM 1 1 Department of Physics, College of Education for Pure Science, University of Babylon, PO Box 4, Hillah-Babylon, Iraq E-mail: Khalid_ik74@yahoo.com 2 Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia Received July 18, 2012 Inelastic electron scattering form factors in some odd-A sd-shell nuclei ( 17 O, 27 Al and 39 K) have been calculated taking into account higher energy configurations outside sd- shell model space, which are called core-polarization (CP) effects. The two-body wildenthal interaction is used for the sd-shell model space. The two-body Michigan three Yukawas (M3Y) interactions are used for the core-polarization CP matrix elements. This interaction was given in LS-coupling. A transformation between LS and jj must performed to get the relation between the two-body shell model matrix elements and the relative and center of mass coordinates, using the harmonic oscillator radial wave functions with Talmi-Moshinsky transformation. The sd-shell model calculations fail to describe the data in both the transition strength and the form factor; the inclusion of CP effects modifies the form factors markedly and describes the experimental data very well in both the absolute strength and the momentum transfer dependence. Key words: Inelastic electron scattering, form factor, Shell model. PACS. 25.30.Bf 25.30.Dh 21.60.Cs 27.20.+n (6 ≤ A ≤ 19) 27.30.+t (20≤ A≤ 38) 1. INTRODUCTION The central problem in nuclear physics has long been the nucleon-nucleon interaction. As it is well known, this interaction is usually described by a potential based on a meson exchange. There are a number of realistic models for potentials. They all describe the nucleon-nucleon scattering data very well [1]. Several theoretical models have been introduced for this purpose, shell-model is one of them and it leads to a very successful description. The sd-shell is considered in the present work, this model deals with only the distribution and coupling of the valence nucleons within a few model-space orbits. According to this model the 16 O is considered as an inert core. The active orbits of the model-space are labeled by the quantum numbers: nlj=1d 5/2 , 2s 1/2 , 1d 3/2 . The nucleons of the core ( 16 O) are 8 protons and 8 neutrons which are inert in the (1s 1/2 ,1p 3/2 ,1p 1/2 ) J=0,T=0 configuration and the remaining A-16 nucleons are distributed over all possible combinations of the 1d 5/2 ,2s 1/2 and 1d 3/2 orbits according to Pauli Exclusion Principle. To investigate Rom. Journ. Phys., Vol. 58, Nos. 3–4, P. 319–329, Bucharest, 2013