Variability and Controls on δ 18 O, d‐excess, and ∆′ 17 O in Southern Peruvian Precipitation

Aron, Phoebe G.; Poulsen, Christopher J.; Fiorella, Richard P.; Levin, Naomi E.; Acosta, Rene P.; Yanites, Brian J.; Cassel, Elizabeth J.

doi:10.1029/2020JD034009

Abstract A simple optical model (OPM) method using non-monotonic (NM) potentials characterized by a repulsive core from the microscopic theory of the Pauli-led energy-density functional (EDF) has been developed to investigate the¹⁶O+¹⁶O fusion at sub-Coulomb energies relevant to the oxygen burning. The study involves the analysis of the experimental fusion cross-section (FCS) data in energy range 6.92 ≤E_cm≤ 13.83 MeV, which includes the Coulomb barrier regionE_cm= 10.0–11.92 MeV. Apart from an excellent description of the existing FCS data in the studied energy range, the associated hindrance, characterized by theS-factor reaching a maximum and then gradually falling off at lower energies, so far suggested empirically for the system, is reproduced down to 4 MeV for the first time in the simple OPM. AnS-factor maximum ofS₀ = 3.15 × 10²⁵MeV.b atE₀ = 7.14 MeV is observed withT ≃ 2.6 GK, which conforms to the values reported for quiescent and explosive burning. Our reaction rate, deduced from the NM potential, compares well with the Caughlan and Fowler data. Dominant partial waves implicit in the observed maximumS-factor in the studied Gamow range are also explored. Our present findings, with the success of NM potentials, suggest thatthe nucleus–nucleus potential is non-monotonic.

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