Strength measurements of the 𝐸labR=647 and 1842 keV resonances in the 40 Ca ⁢(𝑝,𝛾)⁢ 41 Sc reaction and their relevance in novae nucleosynthesis

Here we report on the direct measurement of the resonance strengths of the 𝐸labR=647keV and 1842 keV resonances in the 40 Ca ⁢(𝑝,𝛾)⁢ 41 Sc reaction. At novae temperatures, 0.2<𝑇9<0.7, the 40 Ca
⁢(𝑝,𝛾)⁢ 41 Sc reaction is governed by the low energy resonance at 𝐸labR=647keV, whereas the 𝐸lab
R=1842keV resonance serves as a normalization standard for nuclear reaction experiments within the astrophysically relevant energy range. For the 𝐸labR=647keV resonance, we obtain a resonance strength 𝜔⁢𝛾=(2.51±0.09stat±0.22syst)⁢meV, with an uncertainty a factor of 2.5 smaller than the previous direct measurement value. For the 𝐸labR=1842keV resonance, we obtain a resonance strength 𝜔⁢𝛾=(0.148±0.006stat±0.013syst)⁢eV, which is consistent with previous studies but deviates by 2⁢𝜎 from the most recent measurement. Our results suggest 40 Ca to be a strong waiting point in the nucleosynthesis path of oxygen-neon (ONe) novae.