β-delayed α decay of 16N

The beta-delayed alpha decay of N-16 has been used to restrict the E1 fraction of the ground state gamma transition in the astrophysically important C-12(alpha,gamma)O-16 reaction in several experiments. A review of the published measurements is given, and GEANT4 simulations and R-matrix calculations are presented to further clarify the observed alpha spectra. A clear response function, in the form of a low-energy tail from the scattering of alpha particles in the catcher foil, is observed in these simulations for any foil thickness. Contrary to claims in the literature, the simulations show that the TRIUMF measurement and those performed at Yale and Mainz originate from the same underlying spectrum. The simulations suggest that the discrepancies between the Yale and TRIUMF final results can be attributed to incorrect deconvolution methods applied in the former case. The simulations show in general that the form (width) of the spectrum is very sensitive to the catcher foil thickness. It is concluded that the TRIUMF measurement most likely represents the currently closest approximation to the true beta-delayed alpha-decay spectrum of N-16.