1. JINA Froniters Workshop August 21 st 2005 Searching for Isomers along the rp-Process Path Andreas Wöhr Institute for Nuclear Structure and Astrophysics University of Notre Dame

2. JINA Froniters Workshop August 21 st 2005 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 ♣  + -decay half-lives etc...

3. JINA Froniters Workshop August 21 st 2005 X-ray flux Time [s] 0 200

4. JINA Froniters Workshop August 21 st 2005 -The waiting points can be easily seen from the abundance movie -Slow reactions: -extended energy production -abundance accumulation (steady flow approximation Y=const or Y ~ 1/ ) Waiting Point

5. JINA Froniters Workshop August 21 st 2005

6. 72 Br 68 Se 67 As 68 As 70 Kr 69 Br 69 Se 71 Kr 70 Br 71 Br 72 Kr 73 Rb 74 Rb 73 Kr 67 As+p 68 Se+p 69 Br+p 70 Kr 68 As  exp(Q/kT)* Detailed View at Waiting-Point

7. JINA Froniters Workshop August 21 st 2005

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

9. JINA Froniters Workshop August 21 st 2005 The Experimental Setup at ND beam

10. JINA Froniters Workshop August 21 st 2005 The Situation in 64 Ge predictetd 0 + State not yet seen! (Y. Sun 2005) „kind of“ similar situation to 68 Se 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 0+0+ E(0)

11. JINA Froniters Workshop August 21 st 2005 Preliminary Data from Recent Experiment Gate on 511 keV line neutron  coincidences 2neutron  coincidences

12. JINA Froniters Workshop August 21 st 2005 Total Projection of  -Coincidences

13. JINA Froniters Workshop August 21 st 2005 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  -transition to the 902 keV state in 64 Ge a conversion electron spectrometer has to be used.

14. JINA Froniters Workshop August 21 st 2005 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) Sergio Almaraz-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