Elastic scattering and reaction mechanisms for the system 7Be+28Si at near barrier energies (Doctoral thesis)

Σγουρός, Ονούφριος

The present work refers to the study of elastic scattering and reaction products for the system 7Be + 28Si at near barrier energies, namely 13.2, 17.2, 19.8 and 22.0 MeV (E/VC.b.=1.14, 1.48, 1.71, 1.90). The goal of this work is to probe the energy dependence of the optical potential as well as the interplay between direct and compound nucleus mechanisms. The experiment was visualized at the EXOTIC beam line of the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro (INFN-LNL) in Italy. The various ejectiles were collected by six ΔE-E telescopes of the detector array of the EXOTIC facility, EXPADES, placed at symmetrical position to balance any beam divergence and to improve the statistics of the measurement. The elastic scattering data were analyzed into the optical model framework, following the same method as adopted previously for 6,7Li + 28Si. Comparisons between 7Be-present data and 6,7Li-previous data on the same target showed that, that both mirror nuclei, 7Li and 7Be present the same energy dependence of the optical potential. The behavior of imaginary part of the optical potential is compatible with the standard threshold anomaly, while the real part cannot be definitely interpreted into dispersion relations framework, due to the limited data points around Coulomb barrier. The reaction data were analyzed in both statistical model and Distorted Wave Born Approximation frameworks (DWBA) in order to disentangle the degree of competition between direct and compound channels. The energy evolution of the ratio of direct to total reaction cross section was mapped in comparison with similar data for 6Li and 7Li projectiles on a 28Si target, indicating larger transfer contributions for 7Be and 7Li than in the 6Li case. Fusion cross sections for the system under study were deduced and were found to be compatible with systematic as well as with the Universal Fusion Function (UFF). Moreover, ratios of fusion functions for 6Li to those for 7Li and 7Be were formed, indicating a hindrance of fusion for 7Li and 7Be with respect to those of 6Li below the barrier rather than an enhancement. This hindrance was also observed before for 7Li on various targets and together with the results obtained from our optical model analysis present a strong evidence for the similarity of 7Be with its mirror nucleus 7Li and not the 6Li one.
Institution and School/Department of submitter: Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Φυσικής
Subject classification: Πυρηνική φυσική
Nuclear physics
Keywords: Πυρηνική Φυσική,Πυρηνικές αντιδράσεις,Ασθενικά δέσμιος πυρήνας,Ραδιενεργή δέσμη σωματιδίων,Ελαστική σκέδαση,Μηχανισμοί αντιδράσεων,Συνολική ενεργός διατομή αντίδρασης,Ενεργός διατομή σύντηξης,Υπολογισμοί στα πλαίσια του οπτικού μοντέλου,Υπολογισμοί CDCC,Προσομοιώσεις Monte Carlo,Nuclear Physics,Nuclear Reactions,Weakly bound nucleus,Radioactive beam,Elastic scattering,Reaction mechanisms,Total reaction cross section,Fusion cross section,Optical model calculations,CDCC Calculations,Monte Carlo simulations
URI: http://olympias.lib.uoi.gr/jspui/handle/123456789/28021
Appears in Collections:Διδακτορικές Διατριβές

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