Abstract
The photodisintegration reaction cross-sections for 94Mo(γ,n) and 90Zr(γ,n) have been experimentally investigated with quasi-monochromatic photon beams at the High Intensity γ-Ray Source (HIγS) facility, Triangle University Nuclear Laboratory (TUNL). The measurements were focused primarily on studying the energy dependence of the photoneutron cross sections, which is the most direct way of testing statistical models, and were performed close to the respective neutron thresholds and above up to ~ 20 MeV. Neutrons from the (γ,n) reactions were detected using a 4π assembly of 3He proportional counters developed at Los Alamos National Laboratory and presently available at TUNL. While the 94Mo(γ,n) cross section measurement aims to contribute to a broader investigation for understanding the γ-process (the mechanism responsible for the nucleosynthesis of the so-called p-nuclei), the information from the 90Zr(γ,n) data is relevant to constrain QRPA calculations of γ-ray strength functions in this mass region. In this contribution, we will present our preliminary results of the total (γ,n) excitation functions for the two photoneutron reactions on 94Mo and 90Zr.
Highlights
How nuclear reactions that occur in stars and stellar explosions have been forging the elements out of hydrogen and helium leftover from the Big Bang is a longstanding, still timely research topic in nuclear astrophysics [1]
There is fairly complete understanding of the production of elements up to iron by nuclear fusion reactions in stars, important details concerning the production of the elements beyond iron remain puzzling
Current understanding is that the nucleosynthesis beyond iron proceeds mainly via neutron capture reactions and subsequent - decays in the s-process and r-process [2]
Summary
How nuclear reactions that occur in stars and stellar explosions have been forging the elements out of hydrogen and helium leftover from the Big Bang is a longstanding, still timely research topic in nuclear astrophysics [1]. It is of substantial interest to develop models of the microscopic type which are expected to provide a reasonable reliability and predictive power for the E1strength function Attempts in this direction, such as QRPA calculations [7,8], have been applied successfully to several photoneutron cross section measurements carried out recently with quasi-monochromatic laserCompton scattering rays [9,10,11,12]. The isotope 94Mo is obtained with a much lower abundance with respect to all the other light p-nuclei Another remarkable finding of [13] points out that the -process can make important contributions to the production of the neutron magic 90Zr, previously known as genuine s-process nuclide. In light of the intriguing findings of [13], we were motivated to investigate 94Mo and 90Zr, and in this contribution, we will present our preliminary results of the total (γ,n) excitation functions for the two photoneutron reactions
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