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Searching for Isomers along the rp-Process Path

Searching for Isomers along the rp-Process Path. Andreas W öhr Institute for Nuclear Structure and Astrophysics University of Notre Dame. About the rp-Process. The site of the rp-process are most likely X-ray binaries. There the full rp-process can run

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Searching for Isomers along the rp-Process Path

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  1. Searching for Isomers along the rp-Process Path Andreas Wöhr Institute for Nuclear Structure and Astrophysics University of Notre Dame

  2. About the rp-Process • The site of the rp-process are most likely X-ray binaries. There • the full rp-process can run • but is unlikely to contribute to nucleosynthesis • Experimental information is available form X-ray astronomy. • Model calculations can be performed. However, lots of nuclear physics input is needed: • Masses  reaction Q-values • nuclear level densities • b+-decay half-lives etc...

  3. X-ray flux 200 0 Time [s]

  4. Waiting Point • The waiting points can be easily seen from the abundance movie • Slow reactions: • extended energy production • abundance accumulation (steady flow approximation lY=const or Y ~ 1/l)

  5. 67As+p 71Kr 68Se 67As 68As 69Br 69Se 70Kr 70Br 71Br 73Rb 74Rb 73Kr 72Br 72Kr 69Br+p b+ 68Se+p 70Kr 68As Detailed View at Waiting-Point exp(Q/kT)*<pe,g>

  6. Experiments Performed • 68Se:58Ni(12C,2n)68Se @ 43 MeV • we have seen, the b+-decay products of 68Se and 68As • there is some evidence, that we see states in 68Se • 64Ge:54Fe(12C,2n)64Ge @ 36 MeV • in an experiment finished last Monday morning, we have evidence, that we have seen the b+-decay-products of 64Ge and 65Ge as well as the other reaction channels. • the yield of 64Ge is about 1% of the total yield. • it has to be determined if we have seen states in 64Ge with sufficient statistics.

  7. The Experimental Setup at ND beam

  8. 0+ E(0) The Situation in 64Ge • predictetd 0+ State not yet seen! (Y. Sun 2005) • „kind of“ similar situation to 68Se • E(0) transition will not be seen in this experiment ! • if there the isomers lies not above the 2+ level. Conversion electron spectroscopy needs to be performed

  9. Preliminary Data from Recent Experiment Gate on 511 keV line neutron g coincidences 2neutron g coincidences

  10. Total Projection of gg-Coincidences

  11. Preliminary Conclusion(s) • A lot of things have to be done to find these isomers. • In the presented case the technique with neutron-gamma coincidences has worked to select the neutron reaction channels. • If there is no evidence for a delayed g-transition to the 902 keV state in 64Ge a conversion electron spectrometer has to be used.

  12. The Student on the Project: Timo Griesel (Universities of Mainz and Notre Dame) Producer: Ani Aprahamian (University of Notre Dame and JINA) Co-Producer: A.W. The Crew and Tandem Operators: Plamen Boutachkov (University of Notre Dame) SergioAlmaraz-Calderon (University of Notre Dame) Beverly Lau (Reed College, REU student at Notre Dame) Matthew Quinn (University of Notre Dame) Boris Skoromudov (University of Notre Dame) Theory Support: Yang Sun (University of Notre Dame) Targets: John Greene (Argonne National Laboratory) Spiritual Support: Kim Lister (Argonne National Laboratory) Karl-Ludwig Kratz (University of Mainz) Sponsors: University of Notre Dame National Science Foundation Joint Institute of Nuclear Astrophysics (JINA) Johannes Gutenberg Universität Mainz Vistars The End

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