Decay Studies of Neutron Deficient Antimony Near the Endpoint of the rp-Process

The rp-process or rapid proton capture process, produces nuclei through a series of proton capture or (p,gamma) reactions and beta+ decays along the proton drip-line and above the line of beta stability. In astrophysical models, the rp-process on accreting neutron stars produces energy output in general agreement with light curves from type I X-ray bursts. For some bursts, the resulting reaction network can extend up to the region of the closed nuclear shell at Z = 50. Further progress is prevented due to the &agr; decay of the light Te isotopes resulting in a Sn-Sb-Te cycle.;Models of the rp-process require accurate input from thermonuclear reaction rates and decay half-lives in order to produce results which can be compared to observations. This dissertation describes a 2003 experiment designed to reduce uncertainties in the decay properties of neutron deficient Sb isotopes beyond the proton drip-line and in the vicinity of the Sn-Sb-Te cycle. In this study, the Sb isotopes were produced through the fragmentation method at the National Superconducting Cyclotron Laboratory (NSCL). In this experiment, a 140 MeV/nucleon 124Xe beam impinged upon a Be target. The fragments of the secondary beam were separated in the recently commissioned NSCL A1900 fragment separator and selected nuclei were implanted in a position-sensitive double-sided silicon strip detector (DSSD). The DSSD is the primary detector in the NSCL's beta decay endstation, where both the implanted nuclei and their subsequent decays were observed and correlated within the analysis software.;Due to limitations at the NSCL at that time, it was not possible to eliminate many unwanted fragments from the beam. Several isotopes were implanted at rates three or more orders of magnitude greater than those of the Sb isotopes of interest. Some of these had decay half-lives on the order of minutes or longer. The high rate of implantation by these nuclei created a large and persistent beta decay background within the data that presented itself as time-dependent when correlated to implanted nuclei.;This dissertation describes how implanted nuclei were separated within the analysis and presented onto a 2-D particle identification spectrum (PID). It explains how decays were correlated to implanted nuclei of a given isotope, and how the background decays were characterized and predicted at high precision with a parameterized model. It then describes a curve-fitting procedure to measure the decay half-lives.;Results include a remeasurement of the 104Sb half-life that is in agreement with previous values. A grouping of implantations on the PID presented as a possible observation of the previously unmeasured isotope, 103Sb. Investigation of the resulting decay curve, however, suggests that this spectrum may largely be the result of contamination from 101Sn, which could not be sufficiently resolved from the lightly produced 103Sb within the A1900 at that time.;The results of this study are presented in the context of other recent observations. The on-going development of experimental techniques and their applicability to recent and future decay studies are also discussed.