Evidence for O 15 +α resonance structures in Ne 19 via direct measurement

States in the astrophysically important 19Ne nucleus have been populated directly using the 15O(α,α)15O reaction with a radioactive 15O beam. Due to the challenges involved, this represents the first such 15O measurement with high resolution and the first dedicated to exploring the cluster structure. This measurement comprises three experiments: the first to develop the 15O radioactive beam, the second the resonant scattering study, and the third to measure the precise energy loss of O ions in 4He to reduce systematic uncertainties. The results show evidence for 15O+α cluster structure which could explain earlier results pointing to the increased α branching ratio in the astrophysical reaction rate for high-spin near-threshold resonances. Absolute differential cross sections have been measured. Additionally, spins, parities, and partial decay widths, essential for nuclear reaction-rate calculations, have been extracted using an R-matrix analysis.