sd-shell nuclei; magnetic form factors; Nushell; energy levels.
Magnetic electron scattering (𝑀3) form factors with core polarization effects, energy levels and 𝐵(𝑀3) values to 3+ states of the 26Mg nucleus have been studied using shell model calculations. The universal sd of the Wildenthal interaction, universal sd-shell interaction A, universal sd-shell interaction B, are used for the sd-shell orbits. Core polarization effects according to microscopic theory are taken into account by the excitations of nucleons from the (1𝑠1/2 1𝑝3/2 1𝑝1/2) core and also from valence 1𝑑5/2 2𝑠1/2 1𝑑3/2 orbits into higher shells, with $4\hbar \omega$ excitation. In form factor calculations, the universal sd-shell interaction B for the sd-shell is used with the Michigan three-range Yakawa effective NN interaction as a residual interaction for the core polarization calculations. The wave functions of the radial single-particle matrix elements have been calculated using harmonic oscillator potentials. The level schemes are compared with the experimental data up to 9.902 MeV. In this study, very good agreements are obtained for all nuclei. Results from 𝑀3 form factor calculations with the inclusion of core polarization and new 𝑔-factors give good agreement with the experimental data.