Extensive experimental results are presented showing the variation with energy of the absolute angular distributions for the elastic and inelastic scattering of medium energy protons on carbon. For the scattering with $Q=0\mathrm{}$ and $Q=-4.4\mathrm{}$ Mev, angular distributions between 20 deg and 170 deg were obtained for eleven incident proton energies spaced between 14.0 Mev and 19.4 Mev. Distributions for scattering leading to the excitation of the 7.7-Mev and 9.6-Mev states of ${\mathrm{C}}^{12}$ were measured at energies of 16.7, 17.8, and 18.9 Mev. The experimental results are discussed qualitatively in their relation to the predictions of the theories of nuclear reactions. The elastic scattering cross sections are roughly what one might expect from the complex potential theory, but no numerical comparisons have been made. The predominant inelastic scattering is forward, though the angular distributions corresponding to the three levels studied do not resemble each other. In no single case is one of these distributions symmetrical about 90 deg. The simple Bessel-function distributions of the first-order direct interaction theory do not agree well with the data, but only the scattering leading to the 4.4-Mev level of ${\mathrm{C}}^{12}$ is in apparently complete disagreement.

Experimental differential cross sections as a function of energy are also presented for the scattering of protons on hydrogen near 90 deg (center-of-mass system).

• Received 31 August 1956

DOI:https://doi.org/10.1103/PhysRev.105.1311