Successful prediction of total $\alpha$-induced reaction cross sections at astrophysically relevant sub-Coulomb energies using a novel approach

Abstract

The prediction of stellar ($\gamma$,$\alpha$) reaction rates for heavy nuclei is based on the calculation of ($\alpha$,$\gamma$) cross sections at sub-Coulomb energies. These rates are essential for modeling the nucleosynthesis of so-called $p$-nuclei. The standard calculations in the statistical model show a dramatic sensitivity to the chosen $\alpha$-nucleus potential. The present study explains the reason for this dramatic sensitivity which results from the tail of the imaginary $\alpha$-nucleus potential in the underlying optical model calculation of the total reaction cross section. As an alternative to the optical model, a simple barrier transmission model is suggested. It is shown that this simple model in combination with a well-chosen $\alpha$-nucleus potential is able to predict total $\alpha$-induced reaction cross sections for a wide range of heavy target nuclei above $A\gtrsim 150$ with uncertainties below a factor of two. The new predictions from the simple model do not require any adjustment of parameters to experimental reaction cross sections whereas in previous statistical model calculations all predictions remained very uncertain because the parameters of the $\alpha$-nucleus potential had to be adjusted to experimental data. The new model allows to predict the reaction rate of the astrophysically important ${}^{176}$W($\alpha$,$\gamma$)${}^{180}$Os reaction with reduced uncertainties, leading to a significantly lower reaction rate at low temperatures. The new approach could also be validated for a broad range of target nuclei from $A\approx 60$ up to $A\gtrsim 200$.

6 pages, 3 figures; 6 pages supplement with 3 additional figures and 3 tables; Physical Review Letters, accepted for publication

References in corpus (18)

• Subbarrier fusion reactions and many-particle quantum tunneling
• Sensitivity of p-Process Nucleosynthesis to Nuclear Reaction Rates in a 25 Solar Mass Supernova Model
• Further explorations of the alpha-particle optical model potential at low energies for the mass range A=45-209
• Alpha-induced reaction cross section measurements on 151Eu for the astrophysical gamma-process
• Testing the role of SNe Ia for Galactic chemical evolution of p-nuclei with 2D models and with s-process seeds at different metallicities
• Uncertainties in the production of p nuclides in thermonuclear supernovae determined by Monte Carlo variations
• Alpha induced reaction cross section measurements on 162Er for the astrophysical gamma process
• Cross sections of $\alpha$-induced reactions for targets with masses $A\approx 20-50$ at low energies
• Experimental cross sections of 165Ho(α,n)168Tm and 166Er(α,n)169Yb for optical potential studies relevant for the astrophysical γ-process
• Measurement of the 187Re(α,n)190Ir reaction cross section at sub-Coulomb energies using the Cologne Clover Counting Setup
• Role of ($\alpha$,n) reactions under $r$-process conditions in neutrino-driven winds revisited
• Statistical model analysis of $\alpha$-induced reaction cross sections of ${}^{64}$Zn at low energies
• $\alpha$-scattering and $\alpha$-induced reaction cross sections of ${}^{64}$Zn at low energies
• Measurement of (alpha,n) reaction cross sections of erbium isotopes for testing astrophysical rate predictions
• Cross section of $\alpha$-induced reactions on iridium isotopes obtained from thick target yield measurement for the astrophysical $\gamma$ process
• Cross section of $\alpha$-induced reactions on ${}^{197}$Au at sub-Coulomb energies
• Measurement of the ${}^{58}$Ni($\alpha$,$\gamma$)${}^{62}$Zn reaction and its astrophysical impact
• Cross sections at sub-Coulomb energies: full optical model vs.\ barrier transmission for ${}^{40}$Ca + $\alpha$

Cited by in corpus (13)

• Horizons: Nuclear Astrophysics in the 2020s and Beyond
• Constraining nucleosynthesis in neutrino-driven winds: observations, simulations and nuclear physics
• The $\gamma$-process nucleosynthesis in core-collapse supernovae. I. A novel analysis of $\gamma$-process yields in massive stars
• Low Energy measurement of the ${}^{96}\mathrm{Zr}(\alpha ,n{)}^{99}\mathrm{Mo}$ reaction cross section and its impact on weak r-process nucleosynthesis
• First direct measurement of ${}^{59}$Cu(p,$\alpha$)${}^{56}$Ni: A step towards constraining the Ni-Cu cycle in the Cosmos
• Study of the ${}^{22}$Mg waiting point relevant for x-ray burst nucleosynthesis via the ${}^{22}$Mg($\alpha$,$p$)${}^{25}$Al reaction
• Determination of $\alpha$-optical potential for reactions with p-nuclei from the study of ($\alpha$,n) reactions in the astrophysically relevant energy region
• Cross section measurement of the 144Sm(alpha,n)147Gd reaction for studying the alpha-nucleus optical potential at astrophysical energies
• Measurements of the ${}^{96}$Zr($\alpha$,n)${}^{99}$Mo cross section for astrophysics and applications
• Nuclear Reactions in Evolving Stars
• Determination of ${}^{170,172}$Yb($\alpha ,n$)${}^{173,175}$Hf reaction cross sections in a stacked-target experiment
• Bayesian Analysis of the ${}^{86}$Sr$(\alpha ,\alpha )$ Reaction to Constrain the ${}^{86}$Sr$(\alpha ,n)$ Cross Section at Astrophysical Energies
• Astrophysical Reaction Rates for Charged-Particle Induced Reactions on Proton-Rich Nuclides