Spectroscopy of ¹⁹Ne for the thermonuclear ¹⁵O(α,γ)¹⁹Ne and ¹⁸F(p,α)¹⁵O reaction rates

Original · EN

Uncertainties in the thermonuclear rates of the ¹⁵O(α,γ)¹⁹Ne and ¹⁸F(p,α)¹⁵O reactions affect model predictions of light curves from type I X-ray bursts and the amount of the observable radioisotope ¹⁸F produced in classical novae, respectively. To address these uncertainties, we have studied the nuclear structure of ¹⁹Ne over Eₓ = 4.0 - 5.1 MeV and 6.1 - 7.3 MeV using the ¹⁹F(³He,t)¹⁹Ne reaction. We find the Jπ values of the 4.14 and 4.20 MeV levels to be consistent with 9/2⁻ and 7/2⁻ respectively, in contrast to previous assumptions. We confirm the recently observed triplet of states around 6.4 MeV, and find evidence that the state at 6.29 MeV, just below the proton threshold, is either broad or a doublet. Our data also suggest that predicted but yet unobserved levels may exist near the 6.86 MeV state. Higher resolution experiments are urgently needed to further clarify the structure of ¹⁹Ne around the proton threshold before a reliable ¹⁸F(p,α)¹⁵O rate for nova models can be determined.