Measurement of the ²⁷Al(p, α)²⁴Mg fusion reaction at astrophysical energies via the Trojan Horse Method

¹ Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, 95123 Catania, Italy
² Dipartimento di Fisica e Geologia, Università degli Studi di Perugia, 06123 Perugia, Italy
³ Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, 06123 Perugia, Italy
⁴ iThemba Laboratory for Accelerator Based Sciences, Somerset West 7129, South Africa
⁵ Cyclotron Institute and Department of Physics & Astronomy, Texas A&M University, College Station, Texas 77843-4242, USA
⁶ Institut de Physique Nucléaire d’Orsay, UMR8608, IN2P3-CNRS, Université Paris Sud 11, 91406 Orsay, France
⁷ INAF, Observatory of Rome, Monte Porzio Catone (RM), 00077, Italy
⁸ Dipartimento di Fisica e Astronomia“ Ettore Majorana ”, Università degli Studi di Catania, 95123 Catania, Italy
⁹ Facoltà di Ingegneria e Architettura, Università degli Studi“ Kore ”, 94100 Enna, Italy
¹⁰ CSFNSM-Centro Siciliano di Fisica Nucleare e Struttura della Materia, 95123 Catania, Italy
¹¹ Manipal Centre for Natural Sciences, MAHE, Manipal 576104, India

^* e-mail: lacognata@lns.infn.it

Published online: 18 October 2024

Abstract

In astrophysics, the abundance of ²⁶Al is essential for understanding nucleosynthesis in the Milky Way and Galactic core-collapse supernovae rates. Detection methods involve γ-ray lines and comparing ²⁶Mg overabundance with the common Mg isotope in meteorites. Therefore, stable isotopes ²⁷Al and ²⁴Mg play a crucial role and the MgAl cycle affecting aluminum and magnesium production has to be carefully studied. Recent surveys reveal complexities in stellar populations whose understanding may also benefit from better constraining the closure of the MgAl cycle. The ²⁷Al(p, α)²⁴Mg fusion reaction, a key ²⁷Al destruction channel, is central to these scenarios. Due to uncertainties, the Trojan Horse Method is applied, allowing high-precision spectroscopy on the compound nucleus ²⁸Si. It reveals crucial fusion cross section information in the astrophysically relevant energy range. The indirect measurement by means of the ²H(²⁷Al,α²⁴Mg)n process made it possible to assess the contribution of the 84.3 keV resonance and to set upper limits on nearby resonances. This study evaluates the THM recommended rate’s impact on intermediate-mass asymptotic giant branch stars, showing a notable increase in surface aluminum abundance at lower masses due to fusion cross section modification, while ²⁴Mg remains largely unaffected.