Photoproton Reactions In Medium-Weight Nuclei

Abstract

The angular distributions, energy spectra and integrated yields of photoprotons were measured for nine medium-weight nuclei with atomic number between 28 and 50 in order to test the predictions of the Independent Particle Model of nuclear photodisintegration. Thin metallic foils of natural isotopic abundance were irradiated with a bremsstahlung spectrum of energy 22 MeV. The photoprotons emitted by the targets were detected at angles of 45, 60, 90, 120 and 145 degrees with respect to the direction of the photon beam by means of silicon surface barrier detectors. By using pulse amplitude discrimination, pulse heights from the intense electron background were kept below the level of a four MeV proton for most of the target elements. The detection system was calibrated for energy with the alpha particles from a Ra source. Photoproton energy spectra were thus obtained at each of the five angles of observation for each of the nine target elements. The results of the measurements are discussed in terms of the "resonance direct" interaction theory of Wilkinson. It is found that some extensions to this model are required to explain the experimental data.