JINA Froniters Workshop August 21st 2005
Searching for Isomers along Searching for Isomers along the rp-Process Paththe rp-Process Path
Andreas Wöhr
Institute for Nuclear Structure and Astrophysics
University of Notre Dame
JINA Froniters Workshop August 21st 2005
About the rp-ProcessAbout 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...
JINA Froniters Workshop August 21st 2005
X-r
ay f
lux
Time [s]0 200
JINA Froniters Workshop August 21st 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 PointWaiting Point
JINA Froniters Workshop August 21st 2005
JINA Froniters Workshop August 21st 2005
72Br
68Se
67As 68As
70Kr
69Br
69Se
71Kr
70Br 71Br
72Kr
73Rb 74Rb
73Kr67As+p
68Se+p
69Br+p
70Kr
68As
exp(Q/kT)*<pe,>
Detailed View at Waiting-PointDetailed View at Waiting-Point
JINA Froniters Workshop August 21st 2005
JINA Froniters Workshop August 21st 2005
Experiments Performed Experiments Performed
• 68Se: 58Ni(12C,2n)68Se @ 43 MeV– we have seen, the +-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 +-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.
JINA Froniters Workshop August 21st 2005
The Experimental Setup at NDThe Experimental Setup at ND
beam
JINA Froniters Workshop August 21st 2005
The Situation in The Situation in 6464GeGe• 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
0+
E(0)
JINA Froniters Workshop August 21st 2005
Preliminary Data from Recent ExperimentPreliminary Data from Recent Experiment
Gate on 511 keV line
neutron coincidences
2neutron coincidences
JINA Froniters Workshop August 21st 2005
Total Projection of Total Projection of -Coincidences-Coincidences
JINA Froniters Workshop August 21st 2005
Preliminary Conclusion(s)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 64Ge a conversion electron spectrometer has to be used.
JINA Froniters Workshop August 21st 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