Bonn 2010 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 55: Nukleare Astrophysik III

HK 55.8: Vortrag

Donnerstag, 18. März 2010, 18:45–19:00, HG VI

Lifetime measurements of excited nuclear states of astrophysical interest via the Doppler Shift Attenuation Method — •Clemens Herlitzius and Shawn Bishop — Physik Department E12, TU München, Germany

The production of heavy elements in nova explosions and other events of astrophysical interest are determined by rates of resonant (p,γ) reactions. Because there is always a competition of productive and destructive reactions, these rates are of high interest to predict final elemental abundances with nuclear network calculations. Nuclear inputs from rate measurements, therefore serve to improve models. Resonant reaction rates can be determined with the knowledge of spins, branching ratios and energy levels / lifetimes of excited states of involved product nuclei. The Doppler Shift Attenuation Method (DSAM) is a known technique to measure lifetimes of excited states in the range of fs up to ps. The energy of a Doppler shifted γ-ray, which is emitted by a decelerating de-exciting nucleus, will be measured with a HPGe detector. The lifetime can then be extracted from the γ energy spectrum. A DSAM facility to measure lifetimes of astrophysical interest is being built by the astrophysics group at TU Munich, and first tests and experiments are planned for this year. A study of 34Cl via 34S(3He,t) will be used to understand the detector/electronic system. Known lifetimes of several 34Cl states will serve as calibration references, and new data of unknown states will be measured.

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