Measurement of the branching ratio for beta-delayed alpha decay of 16N

TL;DR

This paper presents a new measurement of the beta-delayed alpha decay branching ratio of 16N, which impacts the extrapolation of the astrophysically important 12C(a,g)16O reaction rate.

Contribution

The authors remeasured the beta-alpha branching ratio of 16N using a segmented Si detector, providing a more accurate value that influences nuclear astrophysics models.

Findings

Branching ratio measured as 1.49(5)e-5, 24% higher than previous value.

Result implies a 14% increase in the extrapolated S-factor for 12C(a,g)16O.

Enhanced accuracy in nuclear reaction rate estimations for astrophysics.

Abstract

While the 12C(a,g)16O reaction plays a central role in nuclear astrophysics, the cross section at energies relevant to hydrostatic helium burning is too small to be directly measured in the laboratory. The beta-delayed alpha spectrum of 16N can be used to constrain the extrapolation of the E1 component of the S-factor; however, with this approach the resulting S-factor becomes strongly correlated with the assumed beta-alpha branching ratio. We have remeasured the beta-alpha branching ratio by implanting 16N ions in a segmented Si detector and counting the number of beta-alpha decays relative to the number of implantations. Our result, 1.49(5)e-5, represents a 24% increase compared to the accepted value and implies an increase of 14% in the extrapolated S-factor.