Abstract
We have performed a detailed γ-ray spectroscopy study of the nucleus, 49Mn, using the GRETINA tracking array and FMA recoil separator. With this powerful new setup, low-spin excited states, which are most relevant for astrophysical processes, have been identified for the first time, including four proton-unbound levels, corresponding to key astrophysical resonances in the 48Cr(p,γ)49Mn reaction. Of these four levels, two were found to dominate the 48Cr(p,γ)49Mn reaction for temperatures, T = 0.2 − 1.4 GK, and uncertainties in the rate have been reduced by more than 3 orders of magnitude. Specifically, γ decays were observed from 1/2+ and 3/2− excited states at Ex = 2570.9(26) keV and 2595.8(21) keV, corresponding to an ℓ = 0 and ℓ = 1 resonance in the 48Cr + p system at Er = 482.9(84) keV and 507.9(83) keV, respectively. Present simulations of Type-I X-ray burst nucleosynthesis indicate that the newly defined 48Cr(p,γ) reaction rate is sufficiently fast to drive the flow of material towards higher masses in such environments. Consequently, despite the relatively long half life of 48Cr, we now do not expect a strong waiting point in the rp process at A = 48.