The masses of proton-rich isotopes of niobium, molybdenum, technetium, ruthenium and rhodium and their influence on the astrophysical rp and vp processes.

摘要

The Canadian Penning Trap mass spectrometer located at Argonne National Laboratory has been built for the purpose of studying the masses of both stable and unstable nuclides. For this thesis 18 proton-rich unstable nuclides of elements Nb, Mo, Tc, Ru and Rh have been measured with this apparatus to an average precision of 7.8 x 10-8. The masses of 6 of these nuclides had not been measured when this thesis was undertaken, and 4 more were not known to the precisions required for use in astrophysical nucleosynthesis models. The masses of these nuclides were of particular interest as the reaction paths of two proposed nucleosynthetic processes, the rp and vp processes, pass through this region. The rp process is thought to occur in X-ray bursts and directly affects the X-ray luminosity which is emitted from these objects. The vp process is thought to occur in the inner regions of the material ejected during a core-collapse supernova explosion and is of particular interest as it may answer some outstanding questions about the origins of the chemical elements in the Universe. The Canadian Penning Trap and associated apparatus were used to determine the masses of 18 nuclides, some for the first time ever. Our measurements improve the precision on all of the masses, by a factor of 70 in some cases. Our results are necessary to determine the proton-separation energies for these nuclides which are critical for determining the paths and reaction rates fro the rp and vp processes. In particular, the effect of our measurements of 92Ru and 93Rh on the expected production ratio of 92Mo to 94Mo in the vp process, and the effect of our measurement of 87Mo on the path of this process will be discussed.