Heavy Element Nucleosynthesis

The production of some of the heavy elements beyond iron occurs by what is called the slow neutron-capture process (the s-process). For the s-process to occur the neutron density needs to be low enough that when a nucleus captures a neutron -- which most likely forms an unstable nucleus -- the new isotope has time to decay back to stability before the next neutron is absorbed. In this way, heavy elements from iron to lead can be produced. The s-process is observed to happen in the final phase of the life of low-mass stars, with alpha-captures on to carbon-13 nuclei providing the source of neutrons. However, for this to work one must first produce a pocket of carbon-13 in the star and at present we do not know how to do this. In this project, the student will use a nucleosynthesis code to investigate the nature of the carbon-13 pocket needed to produce the s-process. They will determine how the size and shape of the pocket affects the production of the s-process nuclei. This will then allow us to examine what physical processes might be responsible for the formation of the carbon-13 pocket.

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