Resonance strengths in the 14N(p,γ)15O and 15N(p,αγ)12C reactions

The N-14(p,gamma)O-15 reaction is the slowest reaction of the carbon-nitrogen-oxygen cycle of hydrogen burning in stars. As a consequence, it determines the rate of the cycle. The N-15(p,alpha gamma)C-12 reaction is frequently used in inverse kinematics for hydrogen depth profiling in materials. The N-14(p,gamma)O-15 and N-15(p,alpha gamma)C-12 reactions have been studied simultaneously, using titanium nitride targets of natural isotopic composition and a proton beam. The strengths of the resonances at E-p = 1058 keV in N-14(p,gamma)O-15 and at E-p = 897 and 430 keV in N-15(p,alpha gamma)C-12 have been determined with improved precision, relative to the well-known resonance at Ep = 278 keV in N-14(p,gamma)O-15. The new recommended values are omega gamma = 0.353 +/- 0.018, 362 +/- 20, and 21.9 +/- 1.0 eV for their respective strengths. In addition, the branching ratios for the decay of the E-p = 1058 keV resonance in N-14(p,gamma)O-15 have been redetermined. The data reported here should facilitate future studies of off-resonant capture in the N-14(p,gamma)O-15 reaction that are needed for an improved R-matrix extrapolation of the cross section. In addition, the data on the 430 keV resonance in N-15(p,alpha gamma)C-12 may be useful for hydrogen depth profiling.