Astrophysical [ital S] factor of [sup 12]C([alpha],[gamma])[sup 16]O from the beta-delayed alpha-particle emission of [sup 16]N

The spectrum of low energy beta-delayed alpha-particle emission of [sup 16]N was measured with high sensitivity; e.g., at [ital E][sub [alpha]][sup [ital L]][approx]1 MeV, a sensitivity for a beta-decay branching ratio in the range of 10[sup [minus]9] (to 10[sup [minus]10]) was achieved. We used previous theoretical work of Ji, Filippone, Humblet, and Koonin to extract from these data the astrophysical [ital p]-wave [ital S] factor for the [sup 12]C ([alpha],[gamma])[sup 16]O capture reaction, and find [ital S][sub [ital E]1](300)=95[plus minus]6(stat)[plus minus]28(syst) keV b. This result is crucial, for example, for understanding the last stages of a massive star before a supernova.