Measurement of ²³Mg(p,γ)²⁴Al resonance energies

The existence of two systematically inconsistent sets of measurements of the ²⁴Al excitation energies, which are used to determine ²³Mg+p resonance energies, results in a variation of a factor 5 in the thermonuclear ²³Mg(p,γ)²⁴Al reaction rate at T=0.25 GK. The astrophysically important energies have been determined to an uncertainty of 6 keV by measuring triton spectra from the ²⁴Mg(³He,t)²⁴Al reaction at E(³He)=30 MeV, and good general agreement is found with one previous set. The present measurement of E_x=2346(6) keV for what is thought to be the most important resonance is, however, in disagreement with both prior measurements of 2328(10) and 2369(4) keV, where the latter value belongs to the outlying set. The presently determined resonance energies reduce the related uncertainty in the ²³Mg(p,γ)²⁴Al reaction rate by a factor of ≈3, which will constrain the determination of nuclear flow out of the NeNa cycle, and production of A⩾20 nuclides, in explosive hydrogen burning over a temperature range 0.2<T<1.0 GK.