On the study of nuclear reaction mechanisms using exotic nuclei
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Authors
Ndala, Lucas Vusi
Issue Date
2022-05
Type
Thesis
Language
en
Keywords
Breakup cross section , Elastic scattering cross section , Complete cross section , Continuum-continuum couplings , Exotic nuclei , Proton- and Neutron-halo nucleus
Alternative Title
Abstract
We investigated the breakup dynamics of the 8B + 208Pb, 11Be + 64Zn, 11Be + 208Pb,
37Mg + 208Pb, 15C + 208Pb, 6Li + 209Bi reactions using the continuum discretized coupled
channels (CDCC) method. Additionally, we investigated the interesting few-body reaction
4He2 + 4He ! 4He + 4He + 4He using the CDCC. At a practical level, our choice of these
reactions was in
uenced by the availability of the experimental data on breakup, fusion,
and elastic scattering cross sections on one hand, and of the theoretical data on the other
which will make the comparison of our results easier. At the fundamental level, these
reactions give a window to explore the dynamics of the nuclear reaction mechanisms of
exotic nuclei.
It is found that the breakup cross section at deep sub-barrier energies is enhanced when the
continuum-continuum couplings are included for the 8B + 208Pb reaction. The complete
fusion cross section is also enhanced at sub-barrier energies but suppressed at abovebarrier
energies due to the continuum-continuum couplings. The breakup observables such
as total reaction, fusion and breakup cross sections, become almost independent of the
ground-state binding energy in the limit approaches zero for the 11Be+64Zn reaction.
It is observed that the rst-order perturbation theory can not explain the breakup of
a system whose ground state wave function becomes unbound whereas, in the CDCC
calculation, when the pure scattering wave function is replaced by the square-integral bin
wave functions, the breakup matrix elements have no convergence issues for both 11Be +
208Pb and 37Mg + 208Pb reactions. We found that the continuum-continuum couplings
and higher-order multipole transitions strongly suppress the nuclear breakup cross section
compared to the Coulomb breakup cross section in the reaction of 15C nucleus on heavy
target. It is found that the resonant states are strongly dominant for lower energies while
the non-resonant states are dominant for higher energies for 6Li+209Bi reaction. A strong
effect of the Helium-dimer continuum-continuum couplings is found on the elastic and
dissociation cross sections in the 4He2 + 4He ! 4He + 4He + 4He reaction. We thenconclude that these couplings are as important in atomic reactions as they are in nuclear reactions, and should be given attention in the analysis of reactions involving loosely-bound molecules.