Observation of 15 N + α resonant structures in 19 F using the thick target in inverse kinematics scattering method

Abstract

The spectroscopy of 19 F is of interest for nuclear astrophysics and nuclear structure. In astrophysics, fluorine and the reactions producing and destroying it play a key role in constraining models of stars in different evolutionary stages, such as the asymptotic giant branch (AGB) stars, responsible of the production of about half of the elements heavier than Fe. In nuclear structure, 19 F has been subject to many investigations aiming at the identification of α and more exotic cluster structures. Also, its spectroscopy is very useful to constrain the nuclear properties of the 19 Ne mirror nucleus. In this work, we report on the measurement of the 15 N − α elastic scattering using the thick target inverse kinematics approach, allowing us to span a very large fluorine excitation energy range ( ∼ 6 –10 MeV). The use of 15 N − α scattering proves very useful to study α clustering in 19 F thanks to the likelihood for populating states with such a structure. Indeed, the R -matrix analysis of the measured differential cross sections shows the occurrence of many candidate α -cluster states of 19 F . It also calls for the redefinition of the spin-parity and widths of a number of 19 F states with respect to what reported in the literature.