The resonance triplet at E_alpha = 4.5 MeV in the 40Ca(alpha,gamma)44Ti reaction

TL;DR

This study precisely measures the strengths of a resonance triplet in the 40Ca(alpha,gamma)44Ti reaction, crucial for understanding 44Ti production in supernovae, with implications for astrophysical models.

Contribution

It provides more accurate resonance strengths for the 40Ca(alpha,gamma)44Ti reaction, improving the data used in supernova nucleosynthesis modeling.

Findings

Resonance strengths determined with higher precision.

Data directly impacts reaction rate calculations above 3.5 GK.

Resonance triplet can serve as a reference in future studies.

Abstract

The 40Ca(alpha,gamma)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 a precise knowledge of the 44Ti production rate may help improve supernova models. The 40Ca(alpha,gamma)44Ti astrophysical reaction rate is determined by a number of narrow resonances. Here, the resonance triplet at E_alpha = 4497, 4510, and 4523 keV is studied both by activation, using an underground laboratory for the gamma counting, and by in-beam gamma spectrometry. The target properties are determined by elastic recoil detection analysis and by nuclear reactions. The strengths of the three resonances are determined to omega gamma = (0.92+-0.20), (6.2+-0.5), and (1.32+-0.24) eV, respectively, a factor of two 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.