Elastic Scattering of 20-Mev. Protons by Oxygen and Nitrogen

The absolute angular distributions for 20-Mev. protons elastically scattered by O 16 and N 14 were determined using the external beam of the frequency-modulated cyclotron at the University of California, Los Angeles. The distributions for the two elements were found to be similar except for the appearance of a more pronounced first minimum in the O 16 distribution. The locations of the maxima and minima seem to indicate that simple diffraction effect is responsible for their presence. The cross sections range from about 1 barn per sterad. to 4 mb. per sterad. between 15° and 165° in the laboratory system. The standard deviations due to statistics range from [Formula: see text] to 10%.