The differential cross sections for the inelastic scattering of protons by ${\mathrm{O}}^{16}$ and for the ${\mathrm{O}}^{16}(p,\alpha ){\mathrm{N}}^{13}$ reaction were measured for $E_p$ from 7.18 to 12.90 MeV. A differentially-pumped gas scattering chamber with a solid-state detector was used. Data at ${\theta }_{\mathrm{lab}}={166}^{\circ }{00}^{\prime }$ were taken in energy steps ≤ 5 keV and with a target thickness ≤ 3 keV. Seven other excitation curves were taken for $7.18<~E_p<~10.5$ MeV at ${\theta }_{\mathrm{lab}}={133}^{\circ }{48}^{\prime }$, 116° 34′, 100° 19′, 86° 24′, 61° 36′, 51° 25′, and 33° 47′. These curves were taken with energy steps ≤ 23 keV depending upon the width of the resonance structure. The target thickness was ≤ 3 keV. Data were obtained on the alphas leaving ${\mathrm{N}}^{13}$ in its ground state and on the inelastic protons leaving ${\mathrm{O}}^{16}$ in its first, second, third, and fourth excited states. Evidence was found for the existence of 36 levels in ${\mathrm{F}}^{17}$, the compound nucleus. Below $E_p=10.5\mathrm{}$ MeV, center-of-mass angular distributions were picked from the eight excitation curves and fitted with Legendre polynomials. Levels in ${\mathrm{F}}^{17}$ at the following excitation energies were assigned total widths, spins, and parities as indicated: $E_x=7.73\mathrm{}$ MeV, ${\Gamma }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=0.178\mathrm{}$ MeV, $J^{\pi }={\frac{1}{2}}^{+}$; 8.07, 0.104, ${\frac{5}{2}}^{+}$; 8.2, 0.706, ${\frac{3}{2}}^{-}$; 8.38, 0.011, ${\frac{5}{2}}^{-}$; 8.42, 0.042, ${\frac{7}{2}}^{+}$; 8.72, 0.188, ${\frac{5}{2}}^{+}$; 8.95, 0.122, ${\frac{5}{2}}^{-}$; 9.16, 0.188, ${\frac{3}{2}}^{+}$; 10.05, 0.282, $\frac{7}{2}$. All parity assignments except those for the levels at $E_x=8.95\mathrm{} \mathrm{and} 9.16$ MeV are based on the assumption that the ${\mathrm{F}}^{17}$ level at $E_x=8.2\mathrm{}$ MeV is the mirror of the ${\frac{3}{2}}^{-}$ level in ${\mathrm{O}}^{17}$ at $E_x=7.72\mathrm{}$ MeV.

• Received 5 September 1963

DOI:https://doi.org/10.1103/PhysRev.133.B647