The inelastic scattering reaction <sup>16</sup>0+<sup>12</sup>C has been studied in the centre-of-mass energy region from 37.7 MeV to 51.4 MeV, in a search for evidence for a seven-alpha chain state in <sup>28</sup>Si. The decay products were detected in coincidence at angular separations around 90° in the centre of mass using two position-sensitive strip detectors. Kinematic reconstruction of the quasi-three body final states yielded the differential cross-sections for the decay channels leading to excited states in <sup>12</sup>C, <sup>16</sup>0 and <sup>20</sup>Ne. The excitation functions measured for the <sup>12 C(0+<sub>2</sub>)-<sup>12</sup>C(0+<sub>2</sub>)-U+03B1 and 12<sup>C</sup>(0<sub>2</sub>)-<sup>8</sup>Be-<sup>8</sup>Be final states agree broadly between the three experiments that were performed, but contain no structure. Reaction channels have also been identified leading to the <sup>8</sup>Be-<sup>20</sup>Ne* and <sup>12</sup>C*-<sup>16<sup>0* final states. The cross-sections for the <sup>8</sup>Be-<sup>20</sup>Ne* decay channels, with the <sup>20</sup> Ne in its lowest excited states, have been compared with previous measurements and provide good agreement. However, none of the excitation functions for these channels contain any structure. The absence of structure in any of the final states, that were identified in this study, indicates that a <sup>28</sup>Si chain state is probably not being observed. The same model, that predicts that the seven-alpha chain state should lie in this excitation region in <sup>28</sup>Si, has also been used to assign a six alpha chain structure to a resonance at E<sub>x</sub>=46.6 MeV in <sup>24</sup> Mg. These two results are compared, and possible reasons for the absence of evidence for a <sup>28</sup>Si chain structure are discussed.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:282023 |
| Date | January 1995 |
| Creators | Simmons, Peter Mark |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:37f984ce-da25-4e98-a843-5039c4f406ff |
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