Protons from Several Elements Bombarded with 30-Mev Alpha Particles

Abstract

Thin targets of Al, Cu, Ag and Au were bombarded with the 30-Mev alpha particles and the energy distributions of protons were measured at angular intervals of 10° or 15°. From an analysis of the energy distributions, the angular distributions for each 2-Mev energy interval were obtained. General behaviours of the angular distributions are as follows. (1) The cross-section increases smoothly from back to forward angles. (2) The forward peaking of the cross-section is greater at low excitation energy of the residual nucleus than at high excitation energy. (3) The forward peaking is more pronounced for heavy elements than for light ones except for Au. From an analysis of the energy distributions at 135° in laboratory system, the relative level densities of the residual nuclei were obtained as a function of the excitation energy of the residual nucleus. The curves on semilog plots of the level densities show the parabolic behaviour which is predicted by the level density formula coming from the Fermi gas.