| Popis: |
The O17(p,γ)F18 and O17(p,α)N14 reactions have a profound influence on hydrogen-burning nucleosynthesis in a number of stellar sites, including red giants, asymptotic giant branch (AGB) stars, massive stars, and classical novae. Previously evaluated thermonuclear rates for both reactions carry large uncertainties. We investigated the proton-capture reaction on O17 in the bombarding energy range of Eplab=180-540keV. We observed a previously undiscovered resonance at ERlab=193.2±0.9keV. The resonance strength amounts to (ωγ)pγ=(1.2±0.2)×10-6eV. With this value, the uncertainties of the O17(p,γ)F18 reaction rates are reduced by orders of magnitude in the peak temperature range of classical novae (T=0.1-0.4GK). We also report on a reevaluation of the O17(p,γ)F18 reaction rates at lower temperatures that are pertinent to red giants, AGB stars, or massive stars. The present work establishes the O17(p,γ)F18 reaction rates over a temperature range of T=0.01-1.5GK with statistical uncertainties of 10-50%. The new recommended reaction rates deviate from the previously accepted values by an order of magnitude around T0.2GK and by factors of 2-3 at T |
