The ${\mathrm{O}}^{16}(p, \alpha ){\mathrm{N}}^{13}$ activation cross section was measured from 12 to 18 Mev with an energy resolution of 30 kev. The results are essentially the same as obtained by Whitehead and Foster and Rouse, using poorer resolution except for one very narrow resonance. As the proton energy increases through this resonance, the cross section first rises 7% to a maximum, then drops 33% to a minimum, and finally rises 6%. The peak and valley have a width at half-maximum of 30 kev and the peak and valley are separated by 60 kev. The proton energy at halfway down the drop was determined, using the limp-wire technique, to be 14.600±0.020 Mev. This resonance is well suited for calibration purposes. A qualitative interpretation of the results is made using the "cluster model."

• Received 10 April 1961

DOI:https://doi.org/10.1103/PhysRev.123.1301