Reaction N 15 ( p , γ ) O 16

The reaction ${\mathrm{N}}^{15}(p, \ensuremath{\gamma}){\mathrm{O}}^{16}$ has been studied up to a proton energy of 4 Mev by using a gas target and NaI(Tl) detectors. Above the well-known resonance at a proton energy of 1.05 Mev where the peak cross section is 1 mb, the cross section drops to a minimum of about 8 \ensuremath{\mu}b around a proton energy of 3 Mev and then increases slightly towards the higher energies. There are no pronounced new resonances and in particular the cross section up to a proton energy of about 3 Mev can be largely accounted for in terms of the high-energy tail of the 1.05-Mev resonance. There is no sign of the very strong quadrupole emission which earlier results on the inverse photodisintegration reaction had led one to expect near a proton energy of 2.8 Mev with a peak cross section of about 90 \ensuremath{\mu}b. Over the whole range of proton energy the gamma-ray emission is isotropic to within about 10%, and this suggests that the 13.09-Mev state of ${\mathrm{O}}^{16}$ (the 1.05-Mev resonance) is well described as ${p}^{\ensuremath{-}1}2s$ and probably contains less than 3% in intensity of ${p}^{\ensuremath{-}1}d$.