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