Elastic and Inelastic Scattering of Protons by Oxygen in the Energy Region of 6.9 MeV to 15.6 MeV

Abstract

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 oxygen. For the elastic scattering, angular distributions between 20 deg and 160 deg were obtained for twenty incident proton energies spaced between 6.87 MeV and 15.6 MeV. The absolute angular distributions for the inelastic proton groups, leading to the excitation of about 6 MeV (6.06 and 6.14 MeV) and 7 MeV (6.92 and 7.12 MeV) states of O 16 , were measured at five energies from 11.9 MeV to 15.6 MeV. Although angular distributions vary remarkably with the incident energy, integrated cross section decreases monotonically as incident energy increases. In particular, at E p =15.6 MeV the total inelastic scattering cross section was roughly measured to be 240±40 mb. From this result and the reported results for other reaction cross sections, we may deduce that O 16 nucleus is considerably transparent even for this rather high incident energy, where the mean free path of nucleon in nuclear matter has nearly the minimum value in usual nuclei. The excitation function for the elastic scattering shows appreciably sharp resonances at energies, 7.2, 10.6 and 14.7 MeV, and its gross structure has a large scale resonance of a width about 4 MeV, at incident energy of about 13 MeV. It appears that this resonance is the f -wave giant resonance expected from the shell model.