Spectroscopy of 30P and the abundance of 29Si in presolar grains

The astrophysical 29Si(p,γ) reaction is expected to play a key role in determining the final 29Si yields ejected in nova explosions. Such yields are used to accurately identify the stellar origins of meteoritic stardust and recently, distinctive silicon isotopic ratios have been extracted from a number of presolar grains. Here, the light-ion 28Si(3He,p) fusion-evaporation reaction was used to populate low-spin proton-unbound excited states in the nucleus 30P that govern the rate of the astrophysical 29Si(p,γ) reaction. In particular, γ decays were observed from resonances up to Er=500keV, and key resonances at 217 and 315 keV have now been identified as 2+ and 2− levels, respectively. The present paper provides the first estimate of the 217-keV resonance strength and indicates that the strength of the 315-keV resonance, which dominates the rate of the 29Si(p,γ) reaction over the entire peak temperature range of oxygen-neon novae, is higher than previously expected. As such, the abundance of 29Si ejected during nova explosions is likely to be less than that predicted by the most recent theoretical models.This paper was supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract No. DEAC02-06CH11357 and Grants No. DEFG02-94-ER40834, No. DEFG02-97-ER41041, and No. DEFG02-97-ER41043. U.K. personnel were supported by the Science and Technologies Facilities Council (STFC). This research uses resources of ANL’s ATLAS facility, which is a DOE Office of Science User facility. J.J. acknowledges support by the Spanish MINECO Grant No. AYA2017–86274–P, by the E.U. FEDER funds, and by the AGAUR/Generalitat de Catalunya Grant No. SGR-661/2017. This article benefited from discussions within the ChETEC COST Action (Grant No. CA16117).Peer reviewe