Solar Abundances for Nuclei Beyond Sr: s-, i- or r- Element Nucleosynthesis?

This paper presents the current status of nucleosynthesis for heavy elements beyond strontium, focusing specifically on the mass range 88 ≤ A ≤ 142. We perform a critical comparison of Solar System abundance contributions from two independent perspectives: the slow neutron-capture (s-) process occurring in low-mass Asymptotic Giant Branch stars, and the rapid neutron-capture (r-) process, modeled using a site-independent waiting-point approach based on (n|γ)⇌(γ|n) equilibrium. While the s-process models now incorporate magnetohydrodynamic mixing to form the necessary 13C neutron sources, the r-process is reconstructed through a superposition of three neutron-density components. When adding abundances predicted in these models, we find a remarkably good agreement between the theory and the Solar System, with minor discrepancies arising from specific nuclear uncertainties affecting isotopes such as 98Mo, 102Ru, 106Pd, 118Sn, 135Ba, and 142Ce. Such discrepancies may be attributed to uncertainties in the nuclear inputs used in the calculations and suggest that the contribution of the i-process to the Solar System abundances is likely to become relevant at higher masses, A > 142.