Nucleosynthesis of 26Al in massive stars: New 27Al states above α and neutron emission thresholds

The Al-26 radioisotope is of great importance for understanding the chemical and dynamical evolution of our galaxy. Among the possible stellar sources, massive stars are believed to be the main producer of this radioisotope. Understanding Al-26 nucleosynthesis in massive stars requires estimates of the thermonuclear reaction rates of the Al-26(n, p)Mg-26, Al-26(n, alpha)Na-23, and Na-23(alpha, p)Mg-26 reactions. These reaction rates depend on the spectroscopic properties of Al-27 states above the neutron and alpha thresholds. In this context, the Al-27(p, p')Al-27* reaction was studied at 18 MeV using a high-resolution Enge Split-Pole spectrometer. States from the ground state up to excitation energies of approximate to 14 MeV were populated. While up to the Na-23 + alpha threshold no additional states are observed, we report for the first time 30 new levels above the Na-23 + alpha threshold and more than 30 new states above the Al-26 + n threshold for which excitation energies are determined with an uncertainty of 4-5 keV.