Speaker
Description
The fission process leads to excited states in neutron rich nuclei at high spin and excitation energy. Obtaining new data for nuclear lifetimes and transition probabilities is a step towards a better understanding of the structure of neutron-rich nuclei and nuclear theory, in general. This presentation deals with the use of the Doppler-shift Attenuation Method (DSAM) coupled with the coincidence method, with the goal to present new values for lifetimes in the sub picosecond range of excited states in neutron-rich nuclei of mass \textit{A $\approx$ 100} and \textit{A $\approx$ 140}. These nuclei are produced with good yields in the neutron induced fission of $^{235}$U. In this work, new results will be shown for the high-spin states of $^{104}$Mo and $^{134}$Te, which have not been studied using DSAM before. Complementary results using the coincidence method have been obtained for $^{97,99,100,101,102}$Zr, as well as $^{100,102}$Nb, which were the result of a previous work using the same analytical setup. The related experiment has been done at ILL, using the FIPPS high-resolution $\gamma$-ray spectrometer array, by using a beam of thermal neutrons on a $^{235}$U target, dissolved in a liquid scintillator. In parallel, the \textit{GEANT4} simulation toolkit has been used to reproduce the experimental conditions at FIPPS and create Monte-Carlo generated spectra. Simulations have been performed for different lifetimes and the lifetime of a given nuclear state has been extracted via a $\chi^2$ analysis. $\gamma$ coincidences have been used both in experimental and simulated data to increase the selectivity in the lineshape analysis.
| Type of contribution | Regular Abstract |
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