The Disappearance of Fusion-Fission and the Onset of Multifragmentation.
Abstract
Information about the evolution of momentum transfer and excitation energy in intermediate energy heavy ion collisions of a fissile target was extracted through an analysis of fission fragment folding angles and charged particle production as beam energy is increased. An exclusive measurement of central events is performed using the MSU 4pi Array as an impact parameter filter. For central collisions, a saturation is found in linear momentum transfer but evidence is presented that excitation energy increases steadily with beam energy. The implications of these measurements are discussed. The space time aspects of the collisions are probed using an analysis which is sensitive to the shape of the ellipsoidal flow envelope of the reaction products in momentum space. This event shape analysis is used to determine whether the dominant reaction mechanism is of a sequential -binary or simultaneous nature and was performed in order to determine at what energy the multifragmentation channel becomes the dominant mode of decay. Such a transition is expected to occur when the excitation energy of the system approaches that of the total binding energy of the system. We deduce that 55 AMeV is the lower limit of the bombarding energy at which multifragmentation becomes dominant in this system.
- Publication:
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Ph.D. Thesis
- Pub Date:
- January 1995
- Bibcode:
- 1995PhDT.......107G
- Keywords:
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- Physics: Nuclear