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

States in the astrophysically important 19 Ne nucleus have been populated directly using the 15 O ( α , α ) 15 O reaction with a radioactive 15 O beam. Due to the challenges involved, this represents the first such 15 O measurement with high resolution and the first dedicated to exploring the cluster structure. This measurement comprises three experiments: the first to develop the 15 O radioactive beam, the second the resonant scattering study, and the third to measure the precise energy loss of O ions in 4 He to reduce systematic uncertainties. The results show evidence for 15 O + 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.