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dc.contributor.authorSene, Martyn R.en
dc.date.accessioned2019-02-15T14:21:07Z
dc.date.available2019-02-15T14:21:07Z
dc.date.issued1982
dc.identifier.urihttp://hdl.handle.net/1842/33887
dc.description.abstracten
dc.description.abstractMeasurements have been made of the cross-sections for the reactions ⁷Li(γ, p₀)⁶He and ⁷Li(γ, n₀+n₂²)⁶Li, by detection of ⁶Li and ⁶He ions ejected from thin lithium foils irradiated with electron bremsstrahlung. This technique ensures that only events from two-body breakup are recorded and enables the energy of the photon responsible for a particular event to be determined from the reaction kinematics. Cross -sections are presented for photon energies from 40 to 140 MeV and for nucleon emission angles of 24°, 50°, 78°, 110° and 144° in the centre of mass frame,and the ratios of the cross-sections for the two reactions are obtained free from systematic errors. The general features of the data are: i) angular distributions which are forward peaked for both reactions, this being more pronounced for (γ, p₀), ii) cross -sections which decrease exponentially with photon energy,with a little structure in the (γ, n₀ +n₂) energy spectra at central angles, iii) cross-section ratios of the order of unity, with the (γ, n₀+n₂) cross -sections enhanced over the ( γ, P₀) cross-sections at backward angles and higher photon energies.en
dc.description.abstractComparison with the predictions of the direct knockout model indicate that the (γ, p₀) cross-sections may be explicable assuming no other process contributes; a consistent 'nucleon momentum distribution' is obtained from the data and the shape of the angular distributions and the energy spectrum at 50° are reproduced by the available calculations. There is considerable disagreement, however, between the various calculations over the absolute magnitude of the cross-sections predicted by the model. Comparison with the data suggests that the direct knockout model is not able to account for the observed (γ, n) cross-sections; in particular the forward peaking of the angular distributions. However,a simple PWIA calculation of the (γ, n) / (γ, p) ratio indicates that the disagreement between this model and such data is not as great as has previously been suggested.en
dc.description.abstractA modified quasi-deuteron model is found to correctly predict the general shape of both the energy spectra and the angular distributions of the two reactions and the magnitude and variation with angle of the cross -section ratios. It fails to reproduce the variation of this ratio with photon energy and the structure in the (y,n) energy spectra. It is shown that these failures are, at least, partly due to approximations made in the model to simplify computation.en
dc.description.abstractShortcomings and problems which exist in both of the above models and the applicability of other models which include nucleon-nucleon correlation effects are discussed. Areas requiring further theoretical and experimental study are highlighted.en
dc.publisherThe University of Edinburghen
dc.relation.ispartofAnnexe Thesis Digitisation Project 2019 Block 22en
dc.relation.isreferencedbyen
dc.title⁷Li(γ, P₀) and ⁷Li(γ, n₀+n₂) reactions at photon energies from 40 to 140 MeVen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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