The 16O(p, γ)17F Direct Capture Cross Section with an Extrapolation to Astrophysical Energies

Abstract

The cross section for the direct radiative capture of protons by ¹⁶O has been measured relative to the proton elastic scattering cross section for energies from 800 to 2400 keV (CM). The elastic scattering cross section was normalized to the Rutherford scattering cross section at 385.5 keV. The capture cross section for the reaction ¹⁶O(p,γ)¹⁷F, which plays a role in hydrogen burning stars, has been extrapolated to stellar energies using a theoretical model which gives a good fit to the measured cross sections. The model involves calculation of electromagnetic matrix elements between initial and final state wave functions evaluated for Saxon–Woods potentials with parameters adjusted to fit both elastic scattering data and binding energies for the ground and first excited states of ¹⁷F. Cross sections for capture to the 5/2⁺ ground and 1/2⁺ first excited states of ¹⁷F in terms of astrophysical S factors valid for energies ≤ 100 keV have been found to be: S_5/2+ = (0.317 + 0.0002E) keV b (± 8%); S_1/2⁺ = (8.552 − 0.353E + 0.00013E²) keV b (± 5%).