Space-time Trajectoryapproach I_ Coulomb excitatio_ of GIA_T dipole RESO_A_CE states

Nguan, Hock Seng (2008) Space-time Trajectoryapproach I_ Coulomb excitatio_ of GIA_T dipole RESO_A_CE states. Masters thesis, University of Malaya.

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The relativistic Coulomb excitation process induced by the collision of heavy ions is studied. Various approaches namely the quantum mechanical, semiclassical, and the space-time trajectory approach recently proposed by Dasso et al. (2004) are reviewed. Following this the space-time trajectory approach is compared with the semi-classical approach of Bertulani et al. (1996). These two approaches have been applied to the case of a 40Ca target bombarded by a 208Pb projectile with a range of energy from 500MeV/A to 6GeV/A. Our calculations of the giant dipole resonance (GDR) and double giant dipole resonance (DGDR) excitation cross-sections agree for both approaches. In addition, the validity of the assumption in-plane symmetry used by Dasso et al. (2004) has been verified. The space-time trajectory and semi-classical approaches have also been applied to the case of Coulomb excitation of the projectile nucleus 136Xe incident on a 208Pb target at Elab = 690MeV/A, for which experimental measurements are available. We show that these two approaches give a good agreement with experimental measurement for GDR excitation cross-section at radius parameter R0 = 1.5 fm. The cross-section agreed to within 3% for the space-time trajectory approach, which was an improvement over the 6% obtained using the semi-classical method. However, both approaches fail to reproduce the DGDR excitation cross-section. We also show that an arbitrary reduction of the radius parameter to R0 = 1.2 fm would improve the agreement with experiment for the DGDR excitation but will, at the same time, worsen the agreement for the GDR excitation cross-section. In order to improve the calculations for the DGDR excitation cross-section, we include the anharmonicity term in the expression of the potential energy. However, calculations show that the contribution to the cross-section is very small if renormalization of the GDR frequency is done to match experimental measurement.

Item Type: Thesis (Masters)
Subjects: Q Science > Q Science (General)
Date Deposited: 31 Jul 2013 03:13
Last Modified: 31 Jul 2013 03:13

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