Resonance triplet at Eα=4.5 MeV in the 40Ca(α,γ)44Ti reaction

Abstract

The 40Ca(α,γ)44Ti reaction is believed to be the main production channel for the radioactive nuclide 44Ti in core-collapse supernovae. Radiation from decaying 44Ti has been observed so far for two supernova remnants, and precise knowledge of the 44Ti production rate may help improve supernova models. The 40Ca(α,γ)44Ti astrophysical reaction rate is determined by a number of narrow resonances. Here, the resonance triplet at Eα=4497, 4510, and 4523 keV is studied both by activation, using an underground laboratory for the γ counting, and by in-beam γ spectrometry. The target properties are determined by elastic recoil detection analysis and by nuclear reactions. The strengths of the three resonances are determined to be ωγ=(0.92±0.20), (6.2±0.5), and (1.32±0.24) eV, respectively, a factor of 2 more precise than before. The strengths of this resonance triplet may be used in future works as a point of reference. In addition, the present new data directly affect the astrophysical reaction rate at relatively high temperatures (above 3.5 GK). © 2013 American Physical Society.