Absolute determination of the 22 Na(p,γ) 23 Mg reaction rate in novae

displayed minimal degradation over a ∼20 C bombardment as a result of protective layers. We avoided the need to know the absolute stopping power, and hence the target composition, by extracting resonance strengths from excitation functions integrated over proton energy. Our measurements revealed that resonance strengths for Ep = 213, 288, 454, and 610 keV are stronger by factors of 2.4–3.2 than previously reported. Upper limits have been placed on proposed resonances at 198, 209, and 232 keV. These substantially reduce the uncertainty in the reaction rate. We have re-evaluated the 22 Na(p,γ) reaction rate, and our measurements indicate the resonance at 213 keV makes the most significant contribution to 22 Na destruction in novae. Hydrodynamic simulations including our rate indicate that the expected abundance of 22 Na ejecta from a classical nova is reduced by factors between 1.5 and 2, depending on the mass of the white-dwarf star hosting the nova explosion.