Counting⁴⁴Ti nuclei from the⁴⁰Ca(α,γ )⁴⁴Ti reaction

Among the many production and destruction nuclear reactions that bear on the net⁴⁴Ti yield in the supernova environment, recently highlighted by γ-ray astronomy observations, the α capture on⁴⁰Ca stands out in the α-rich freezeout phase conjectured by astrophysical models. We activate a He-gas target, with a⁴⁰Ca beam and implant recoiling⁴⁴Ti nuclei (∼10⁶) in a Cu catcher. The⁴⁴Ti atoms chemically extracted with a^natTi carrier are counted by accelerator mass spectrometry (AMS). The measurement of the⁴⁴Ti/Ti ratio, together with the amount, of Ti carrier added, determine the number of⁴⁴Ti nuclei produced in the activation, independent, of chemical yield or transmission efficiency. The resonance strength (7.4±2.5 eV) at E_cm∼1.1 MeV/n determined for two close-by levels of⁴⁴Ti is in excellent agreement, with previous prompt-γ measurements. We plan to extend our experiments to the lower energy range.