Proton-decaying states in ²²Mg and the nucleosynthesis of ²²Na in novae

Populating states in ²²Mg via the (p, t) reaction in inverse kinematics with a 55-MeV/nucleon ²⁴Mg beam, we have measured the proton-decay branching ratios of the levels at 5.96 MeV and 6.05 MeV and obtained an experimental upper limit on the branching ratio of the 5.71-MeV state. On the basis of the present and previous measurements, we assign spins and parities to the 5.96-MeV and 6.05-MeV states. We combine our branching ratios with independent measurements of the lifetimes of these states or their ²²Ne analogs to compute the resonance strengths and thereby the astrophysical rate of the ²¹Na(p, γ)²²Mg reaction. We perform hydrodynamic calculations of nova outbursts with this new rate and analyze its impact on ²²Na yields.