R-matrix analysis of the Β-delayed α - spectrum of 16N and the 12C(α, γ)16O reaction

The 12C(α,γ)16O reaction is of considerable importance in the evolution of massive stars, as its rate, relative to the triple α process, determines the relative abundances of 12C and 16O at the end of helium burning. Due to the presence of subthreshold resonances, the precise determination of this cross section at the relevant energy of Ecm=300 keV is extremely difficult. The Β-delayed α-spectrum of 16N allows an improved determination of the El part of this cross section by constraining the reduced α-width of the 1- subthreshold state. This spectrum has recently been remeasured with high statistics down to Ecm=800 keV at the TRIUMF isotope separator, TISOL. The results of extensive R-matrix fits incorporating this new data will be presented