Angular Distributions of 4.43-Mev Gamma Radiation fromC12(p, p′γ)C12

Abstract

The yield at 90 degrees, and 32 angular distributions of the 4.43-Mev gamma ray from the first-excited state of ${\mathrm{C}}^{12}$ have been measured for proton bombarding energies between 5 and 12 Mev. The excitation curve for inelastic scattering is characterized by a number of strong resonances, some of which were previously known. In addition, underlying the resonances, there is a monotonically rising background. The angular distributions were fitted by least squares to the expression $W\left(\theta \right)=A_0+A_2{P}_2\left(cos\theta \right)+A_4{P}_4\left(cos\theta \right)$. Those obtained in the region of the resonances at $E_p=5.36\mathrm{}$ Mev and $E_p=5.89\mathrm{}$ Mev can be interpreted by taking into account these two resonances with respective characters ${\frac{3}{2}}^{+}$ and ${\frac{5}{2}}^{+}$ plus one additional state at an excitation energy of 6.38 Mev (${\frac{5}{2}}^{+}$) in the compound nucleus ${\mathrm{N}}^{13}$ which can be seen only in elastic scattering. A simple direct-reaction model using a nucleon-nucleon interaction accounts very well for four angular distributions at higher energies in regions showing no resonant structure.