Abstract
The 15O(α,γ)19Ne reaction is expected to trigger the initial path for breakout from the CNO hydrogen-burning cycles to the rapid proton capture (rp) process in type I x-ray bursts on accreting neutron stars. The thermonuclear reaction rate has a major impact on models of type I x-ray burst observables and it depends on the small α-particle branching ratio, Γα/Γ, of the 4.03 MeV state in 19Ne. Attempts to measure Γα/Γ by populating the 4.03 MeV state using nuclear reactions have only led to strong upper limits. In the present work, we report the first experimental evidence that the 4.03 MeV 19Ne state is populated in 20Mg β-delayed proton emission. This new channel has the potential to provide the necessary sensitivity to detect a finite value of Γα/Γ.
