Some remarks about the beta-delayed alpha-decay of 16N

TL;DR

This paper reviews and analyzes the beta-delayed alpha-decay spectrum of 16N, using simulations and calculations to clarify experimental discrepancies and suggest the most accurate spectrum measurement.

Contribution

It provides a comprehensive review, GEANT4 simulations, and R-Matrix calculations to resolve inconsistencies in previous measurements of 16N decay spectra.

Findings

Simulations reveal a response-function tail from alpha scattering in catcher foil.

TRIUMF and other measurements originate from the same underlying spectrum.

Discrepancies are due to incorrect deconvolution methods in some experiments.

Abstract

The beta-delayed alpha-decay of 16N has been used to restrict the E1 fraction of the ground state gamma-transition in the astrophysically important 12C(alpha,gamma)16O reaction in several experiments including those performed at TRIUMF and several other laboratories. 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 suggests 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 16N.