Improved characterization of the structure of ¹⁶O above the proton separation energy

The level structure of the ¹⁶O compound system is of particular interest for reactions that determine energy production and nucleosynthesis during the early burning stages in massive stars. During hydrogen burning, the system is populated by both the¹⁵N(p,γ)¹⁶O and ¹⁵N(p,α)¹²C reactions, whose relative cross sections determine one of the branch points in the carbon-nitrogen-oxygen cycle that is the main source of energy production. During the next stage, helium burning, the ¹²C(α,γ)¹⁶O reaction populates this same system. Uncertainty contributions for both of these reactions stem from unknown population strengths of higher energy levels, which remain relatively poorly characterized. We have therefore made a new high precision, thin-target, relative cross section study of ¹²C+α induced reactions over the laboratory α-particle energy range from 7.5 to 11.5 MeV, which extend the range of previous studies. Measurements were preformed using the 2 m scattering chamber at the University of Notre Dame Nuclear Science Laboratory at 28 unique angles between 30 and 170 degrees. Excitation functions for the α₀, α₁, and p₀ channels and preliminary R-matrix calculations will be presented.