The Photonuclear Reactions Leading to 24Na and 28Mg

Abstract

Abstract The photonuclear reaction yields of 24Na and 28Mg in magnesium, aluminum, silicon, phosphorus, and sulfur were obtained at energies between 20 MeV and 250 MeV by the induced radioactivity method. The 12C(γ,n)11C yield was used as a standard for the beam monitor. The excitation curves of the 27Al→24Na, 28Si→24Na, Si30→28Mg, 31P→24Na, 31P→28Mg, 32S→24Na, and 32S→28Mg reactions were obtained from the yields by the photon-difference method. Each of these excitation functions indicates a peak in the 50–70 MeV energy range, except in the case of the sulfur target, in which the peak is due to the contribution from the compound-nucleus process. The interaction of photons with nuclei at photon energies exceeding the peak energy region probably does not lead to the formation of the compound nucleus. In the energy range from 70 MeV up to 150 MeV, the cross sections are due to the contribution from the quasi-deuteron process. At energies above 150 MeV and up to 250 MeV, the quasi-deuteron and pion production processes compete. In the high-energy photonuclear reaction mechanisms, the quasi-deuteron and pion production processes must be considered at the initial cascade process, but the evaporation process may be considered after the cascade process.