Improved S Factor of the 12c(p, ) 13N Reaction at E=320-620 Kev and the 422 Kev Resonance

The 12C(p, & gamma; ) 13N reaction is the onset process of both the CNO and hot CNO cycles that drive massive star, red and asymptotic giant branch star, and novae nucleosynthesis. The 12C(p, & gamma; )13N rate affects the final abundances of the stable 12,13C nuclides with ramifications for meteoritic carbon isotopic abundances and the s-process neutron source strength. Here, an underground measurement of the 12C(p, & gamma; ) 13N cross section is reported. The present data, obtained at the Felsenkeller shallow-underground laboratory in Dresden (Germany), encompass the 320-620 keV center of mass energy range to include the wide and poorly constrained E = 422 keV resonance that dominates the rate at high temperatures. This work's S-factor results, lower than literature by 25%, are included in a comprehensive R-matrix fit, and the energy of the 1 + first excited state of 13N is found to be 2369.6(4) keV with a radiative and proton width of 0.49(3) eV and 34.9(2) keV, respectively. A reaction rate, based on the present R-matrix fit and extrapolation, is suggested.