Energy and angular distributions of photoprotons from ${\mathrm{O}}^{16}$ have been measured using 33-MeV bremsstrahlung from an electron synchrotron. A relative cross section is obtained for photoproton transitions to the ground state of ${\mathrm{N}}^{15}$ in the energy interval of 27-33 MeV. Below 27 MeV, the data include protons from higher-lying levels decaying through excited states, preventing extraction of a valid cross section for this region. Angular distribution data are analyzed in terms of Legendre polynomials. The anisotropy parameter $A_2$ has the value of -0.55±0.2 over the entire energy range, very near the expected value for $d$-wave proton emission from a dipole state. The asymmetry parameters $A_1$ and $A_3$ both increase in absolute value to a maximum at 30.5 MeV. Observed fluctuations in $A_1$ and $A_2$ are well correlated with known resonances in the cross section. The data indicate a broad region of moderate quadrupole strength extending to the upper energy limit of the experiment.

• Received 30 April 1969

DOI:https://doi.org/10.1103/PhysRev.186.992