Thermonuclear reaction rate ofSi29(p,γ)P30

Abstract

The thermonuclear rate of the $^{29}\mathrm{Si}(p,\ensuremath{\gamma})^{30}\mathrm{P}$ reaction impacts the $^{29}\mathrm{Si}$ abundance in classical novae. A reliable reaction rate is essential for testing the nova paternity of presolar stardust grains. At present, the fact that no classical nova grains have been unambiguously identified in primitive meteorites among thousands of grains studied is puzzling, considering that classical novae are expected to be prolific producers of dust grains. We investigated the $^{29}\mathrm{Si}+p$ reaction at center-of-mass energies of $200\text{--}420\phantom{\rule{4pt}{0ex}}\mathrm{keV}$, and present improved values for resonance energies, level excitation energies, resonance strengths, and branching ratios. One new resonance was found at a center-of-mass energy of $303\phantom{\rule{4pt}{0ex}}\mathrm{keV}$. For an expected resonance at $215\phantom{\rule{4pt}{0ex}}\mathrm{keV}$, an experimental upper limit could be determined for the strength. We evaluated the level structure near the proton threshold, and present new reaction rates based on all the available experimental information. Our new reaction rates have much reduced uncertainties compared with previous results at temperatures of $T\ensuremath{\ge}140$ MK, which are most important for classical nova nucleosynthesis. Future experiments to improve the reaction rates at lower temperatures are discussed.