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|Title:||Theoretical Study of Quadrupole Moments and Transition Rates of Some sd-Shell Neutron Rich Nuclei Using Different Model Spaces|
|Other Titles:||دراسة نظرية لعزوم رباعية القطب ومعدلات الانتقال لنوى الغلاف sd الغنية بالنيوترونات بأستعمال نماذج فضاءات مختلفة|
|Authors:||Ahmed Hussein Ali|
|Abstract:||uadrupole moments, quadrupole transition rates and form factors are calculated for some sd and sd-pf cross shell isotopes. For sd-shell nuclei with neutron number N ≤ 20, sd shell model space is used. For neutron rich nuclei (cross shell nuclei) with N > 20, sdpf valence space is used with full sd shell (Z-8) protons and full pf shell (N-20) neutrons. Excitation out of major shell space are taken into account through a microscopic theory which allows particle-hole excitation from the core and model space orbits to all higher orbits with 2 excitation. From the calculations, effective charges are deduced and the quadrupole moments are calculated for Al (A = 23, 25, 26, 27, 28, 31, 32, 33), Si (A = 27, 28, 30, 42), P (A = 28), S (A = 32, 33, 34, 35, 43, 44), Cl (A = 35, 36, 37), Ar (A = 35, 36, 37, 39, 40, 41, 43, 44, 46) and K (A = 37, 39, 40, 41) isotopes. The reduced electric quadrupole transition probabilities for the transition 0+→2+ are calculated for even-even Si (A = 26, 28, 30, 32, 34, 36, 38, 40, 42, 44), S (A = 30, 32, 34, 36, 38, 40, 42, 44, 46) and Ar (A = 34, 36, 38, 40, 42, 44, 46, 48) isotopes. The model spaces that are used with the inclusion of core-polarization effects, which are presented by the core-polarization effective nucleon charges, improve the agreement with the available experimental data remarkably well and play an essential role for electric quadrupole moments and the reduced electric quadrupole transition probabilities. The calculations are also performed using effective charges obtained from Bohr – Mottelson model and also the standard proton and neutron effective charges, and and the results are compared with the available experimental data. Abstract V Good agreement is obtained with the measured data for most of the isotopes considered in this work while it deteriorates for some of them and need further investigation. The Coulomb C2 form factors are also calculated for the transition 0+→ 2+ for the isotopes Si (A = 26, 28, 30, 32, 34, 36, 38, 40, 44), S (A = 30, 32, 34, 36, 38, 40, 42, 44) and Ar (A = 34, 36, 40, 42, 44, 46, 48) using effective charges obtained from core polarization calculations and compared with available experimental data. The results for the reduced transition probabilities show a systematic increase for N 20. Shell model calculation predicts the erosion of the N=28 magicity in the neutron rich 42Si. No clear indications about the erosion of the shell gap closure in 44S and 46Ar isotopes.|
|Appears in Collections:||البحوث العلمية|
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