γ-ray spectroscopy study of states in Si27 relevant for the Al26m(p,γ)Si27 reaction in novae and supernovae

Abstract

The heavy-ion, fusion-evaporation reaction 12 C( 16 O,n) was used to identify γ-decay transitions from excited states in 27 Si above the proton threshold. The precise level energy measurements, J π assignments, and lifetime measurements of astrophysically important 26 Al m + p resonances have allowed an evaluation of the 26 Al m (p,γ) 27 Si reaction rate. An l p = 0 resonance has been newly identified at a center-of-mass energy in the 26 Al m + p system of 146.3(3) keV and is expected to dominate the rate for low stellar temperatures. In addition, an lp = 1 resonance has been identified at 378.3(30) keV and is likely to dominate the rate at high astrophysical temperatures, such as those found in oxygen-neon novae and core-collapse supernovae.