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Breakup of 8B and 8Li.

Mortimer, John. (2001) Breakup of 8B and 8Li. Doctoral thesis, University of Surrey (United Kingdom)..

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Fully three-body kinematical calculations have been developed for analysing the breakup of light, weakly bound two-body projectiles using several theoretical models. Parallel momentum distributions of the 8Be fragments produced in the breakup of on Ag and Pb targets at 44 and 82 MeV/nucleon have been calculated. The asymmetry seen in these distributions due to E1/E2 interference is instructive in trying to understand the El and E2 contributions to the total cross section. The predicted E2 cross section in these reactions was found to be model dependent. Semi-classical first-order perturbation calculations show that an E2 strength of 70% that given by the Esbensen and Bertsch 8B structure model reproduces the asymmetry observed in the measured distributions for a Pb target at 44 MeV/nucleon. Non-perturbative coupled discretised continuum channels (CDCC) calculations gave distributions with a greatly reduced asymmetry when compared with first-order calculations highlighting the presence of higher-order effects in the breakup process, which suppress the E1/E2 interference. Increasing the E2 amplitude by a factor of 1.6 in these calculations reproduced the asymmetry seen in the all measured distributions. Comparisons between the CDCC and adiabatic methods have been made. The adiabatic method is a higher-order theory, like CDCC, but cannot be applied to projectiles where both fragments are charged. Therefore the breakup of 8Li has been studied. Large discrepancies are seen between the results of the two methods. Approximations have been made in evaluating the DWBA post-form T-matrix. The results are similar to those of the adiabatic method, rather than prior-form DWBA calculations. These results reveal a post-prior disagreement in both first-order and higher-order theories.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Mortimer, John.
Date : 2001
Contributors :
Depositing User : EPrints Services
Date Deposited : 09 Nov 2017 12:11
Last Modified : 16 Jan 2019 18:58

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