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I. Fission probabilities, fission barriers, and shell effects. II. Particle structure functions

Posted on:2000-10-02Degree:Ph.DType:Dissertation
University:University of California, BerkeleyCandidate:Jing, KexingFull Text:PDF
GTID:1460390014964050Subject:Physics
Abstract/Summary:
In Part I, fission excitation functions of osmium isotopes 185,186,187,189 Os produced in 3He + 182,183,184,186W reactions, and of polonium isotopes 209,210,211,212Po produced in 3He/4He + 206,207,208Pb reactions, were measured with high precision. These excitation functions have been analyzed in detail based upon the transition state formalism. The fission barriers, and shell effects for the corresponding nuclei are extracted from the detailed analyses.; A novel approach has been developed to determine upper limits of the transient time of the fission process. The upper limits are constrained by the fission probabilities of neighboring isotopes. The upper limits for the transient time set with this new method are 15 x 10-21 sec and 25 x 10-21 sec for Os and Po compound nuclei, respectively.; In Part II, we report on a search for evidence of the optical modulations in the energy spectra of alpha particles emitted from hot compound nuclei. The optical modulations are expected to arise from the alpha-particle interaction with the rest of the nucleus as the particle prepares to exit. Some evidence for the modulations has been observed in the alpha spectra measured in the 3He-induced reactions, 3He + natAg in particular. The identification of the modulations involves a technique that substracts the bulk statistical background from the measured alpha spectra, in order for the modulations to become visible in the residuals. Due to insufficient knowledge of the background spectra, however, the presented evidence should only be regarded as preliminary and tentative.
Keywords/Search Tags:Fission, Spectra
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