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First Stars III
Contact:
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Poster
Title: Global Nuclear-Structure Calculations for Astrophysical Networks Author(s): Peter MOller Abstract: In the macroscopic-microscopic approach we calculate for nuclei from A=16 to A=330 (1) nuclear masses and other ground-state properties, (2) beta-decay and electron-capture rates and beta-delayed neutron emission rates, (3) fission barriers and associated beta-delayed fission rates. We published the FRDM (1992) nuclear mass model in 1995. Its parameters were adjusted to a 1989 experimental mass data base. The model error was 0.67 MeV. Today more than 500 new masses have been measured. The model error is only 0.46 MeV for these new masses. When the FRDM (1992) model is compared to the entire data set now available the model error is about 0.63 MeV. Because of a more than 10000 fold increase in computer power since our previous mass table was published we are now able to perform much more accurate searches for the correct shape of the ground-state minimum and determine the associated mass. We now search the full 4-dimensional space in the variables epsilon_2, epsilon_3, epsilon_4 and epsilon_6. In a separate study we include the effect of triaxial nuclear shapes. This more accurate determination of the ground-state minimum lowers the error to 0.58-0.59 MeV (Calculation is still in progress). We have calculated fission barriers for more than 5000 nuclei in very large 5-dimensional deformation spaces in the FRLDM model Our calculated fission barriers agree much better with observed fission data such as the fission properties of elements in the range Z=107 to Z=113, the three-humped fission barriers of light Th isotopes, and fission barrier heights for sub-actinide nuclei than do the recent HF fission results from the Brussels group. Our integrated model framework allows us to study fission properties at the end of the r-process, and to calculate beta-delayed fission rates in this region. Our microscopic QRPA model of beta decay, which allows us to calculate the beta-delayed fission rates, is also applied to the calculation of beta-decay rates and beta-delayed neutron-emission rates for nuclei in the r-process path and in its decay paths back to stability. Furthermore we calculate log ft matrix elements for electron capture.The model can be applied to both ground-state capture and capture on excited states. Capture rates in stellar environments of extreme temperature and pressure are then calculated based on these log ft values.
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