ISOTOPIC ANOMALIES FROM NUCLEAR PROCESSES IN STARS
Doctor of Philosophy
Specific nucleosynthetic environments are examined as the sources for the anomalous xenon observed in meteorite samples. A simplified nuclear network is used to allow rapid estimation of isotopic abundances over a wide range of stellar conditions. In the zone of oxygen burning outside a stellar core that is in the silicon burning phase of energy generation, photodisintegration of xenon seed isotopes is shown to be a potential source of an overabundance of the p-isotopes of xenon. The result ('124)Xe/('126)Xe > 1 can be obtained if theoretical calculations systematically overestimate photo-alpha emission rates of certain p-isotopes of elements in the xenon region of the chart of the nuclides. Anomalies in the abundances of the heaviest xenon isotopes are shown to be a possible consequence of neutron capture reactions during explosive carbon burning in a supernova. Overabundances of ('136)Xe relative to ('134)Xe are the result of the low neutron-capture rates of N = 82 nuclei and the high photo-neurtron emission rates of N= 38 nuclei. Isotopic abundance signatures in the elements krypton, tellurium and osmium that are correlated with anomalous xenon are shown to be a plausible result of nuclear processing in the same environments that may produce anomalous xenon. The relative abundance of ('129)I associated with anomalous xenon is also examined, and predictions for anomalies in other elements based on the models presented here are given.