Energy Dependence of Elastic and Inelastic Scattering fromC12for Protons between 14 and 19 MeV

Differential cross sections $\sigma (E,\theta )$ for elastic and inelastic (4.43 MeV) proton scattering by ${\mathrm{C}}^{12}$ have been obtained as a continuous function of bombarding energy for 15 scattering angles between 15° and 160°. The energy resolution was approximately 200 keV, and the angular resolution was chosen as $\Delta \theta \le 2^{\circ }$. The data show several resonance-like variations for $\sigma \mathrm{}\left(E\right)\mathrm{}$, <300 to 500 keV wide for all angles observed. Changes in the elastic and inelastic (4.43 MeV) differential cross sections are closely correlated and are strongest near 15 and 17.6 MeV. In the experiment, use was made of the fact that in a thick target the incident energy is reduced by ionization so that scattering occurs over a range of energies $\Delta E$. Consequently, the energy spectrum of the scattered protons can be used to obtain continuous excitation functions $\sigma \mathrm{}\left(E\right)\mathrm{}$ over the energy interval $\Delta E$. In the present measurements, polystyrene targets of $\Delta E=1.6\mathrm{}$ MeV were used. A discussion of the thick-target method is presented. Normalizations and cross checks for the thick-target excitation functions were obtained by conventional thin-target cross section measurements. The latter runs also yielded some cross sections for scattering to the 7.66- and 9.64-MeV states in ${\mathrm{C}}^{12}$. Scattering to the $0^{+}$, 7.66-MeV state showed strong energy dependence while scattering to the $3^{-}$, 9.64-MeV state showed fluctuations of not more than 15%. The scattering cross sections are compared with optical model calculations by Nodvik, Duke, and ${\mathrm{M}\mathrm{e}\mathrm{l}\mathrm{k}\mathrm{a}\mathrm{n}\mathrm{o}\mathrm{f}\mathrm{f},}^{13}$ and ${\mathrm{C}}^{12}(p,p^{\prime }\gamma ){\mathrm{C}}^{12}$ $\gamma$-yield measurements by Warburton and ${\mathrm{Funsten}.\mathrm{}}^{24}$