The effect of pygmy resonances on p-process nucleosynthesis Public Deposited

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  • March 21, 2019
  • Angell, Christopher T.
    • Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
  • The γ-ray strength function (γSF) is a key component for calculating photodisintegration reaction rates used for the simulation of the p-process. During the p-process, the nucleus can be thermally excited lowering the threshold for photodisintegration, thus significantly enhancing the reaction rate for neutron photodisintegration. To calculate the (γ, n) reaction rates for excited states the γSF needs to be known below the neutron separation energy. The presence of a pygmy dipole resonance (PDR) near the neutron separation energy could further enhance the reaction rate. To study the low energy γSF, particularly the PDR, and its dependence on the neutron number, measurements to determine the γSF both above and below the neutron separation energy were done on 142Nd and 150Nd. To determine the γSF above the neutron separation energy the (γ, n) cross sections were measured near threshold for 142Nd, and, for the first time, for 150Nd. The (γ, n) measurements were made using the monoenergetic γ-ray beam at the AIST TERAS facility in Tsukuba, Japan. To determine the γSF below the neutron separation energy a new technique using nuclear resonance fluorescence was developed, and measurements were taken for 142Nd at Eγ= 3.4 – 9.7 MeV, and 150Nd at Eγ= 5.6 – 7.2 MeV. The experiment was performed using a polarimeter consisting of four Clover detectors at the mono-energetic γ-ray beam facility, HIγS, at the DFELL in Durham, NC. The results will be compared to theoretical calculations using the quasi-particle random phase approximation(QRPA), and the neutron number dependence of the low-energy E1 γSF, and the potential effects of the results on the p-process will be discussed.
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  • Karwowski, Hugon
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  • University of North Carolina at Chapel Hill
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