Exploration of the limits in the statistical treatment of the quasicontinuum in 90Zr using complementary methods for the extraction of photon strength functions and nuclear level densities

• Applicant: Dr. Johann Isaak
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572037347

This research project focuses on nuclear level densities and photon strength functions, which are one of the important input quantities for nuclear reaction codes based on the Hauser-Feshbach statistical formalism, necessary for modelling and understanding nucleosynthesis in the Universe. In particular, the region around and below the neutron separation threshold is studied, where nuclear quantum states form a so-called quasicontinuum. It is still unclear to what extent and under what conditions a statistical treatment of nuclear properties is justified in this region. The project aims to study the validity of the statistical model in the quasicontinuum by using advanced experimental methods to measure the nuclear level density and the photon strength function of 90Zr by inelastic proton and alpha scattering. In addition to standard analysis techniques such as the Oslo method, an extended version of the so-called shape method will be applied for the first time to the data to minimize systematic uncertainties from strong assumptions and simplifications inherent in current methodological approaches. Key research questions include the reliability of different measurement methods for determining nuclear level densities and photon strength functions, the applicability of the statistical model in the quasicontinuum of 90Zr, and the implications for stellar reaction rates and element formation in the Universe.

• DFG Programme: Research Grants