Nonresonant capture cross section measurement of the ²⁹Si(<i>p</i>,<i>γ</i>)³⁰P reaction

Abstract The isotopic ratios measured in meteoritic presolar grains are a crucial tool for tracing the nucleosynthetic origin of isotopes. In the case of silicon isotopes, two important indicators to establish the origin of presolar grains are the ratios 29 Si/ 28 Si and 30 Si/ 28 Si. To constrain theoretical predictions, the rates of key nuclear reactions influencing the abundances of 29 Si and 30 Si must be well known. One such reaction is 29 Si( p , γ ) 30 P which plays a role in classical nova explosions. The aim of the present work is to determine the nonresonant cross section of the 29 Si( p , γ ) 30 P reaction, which has not been previously measured. The activation method was employed to measure the total cross section at four proton energies between E p = 1000 and 1430 keV. The measured cross sections were found to be significantly (a factor of 4.3 ± 0.6) higher than those predicted by theoretical direct capture calculations, thereby impacting the reaction rates at low astrophysical temperatures, below about 30 MK. This higher nonresonant cross section—now based on experimental data—can be used in forthcoming nucleosynthesis calculations of classical novae. As a secondary result, the 16 O( p , γ ) 17 F cross section was also obtained and found to be in good agreement with existing literature data.