The inelastic scattering of protons by magnesium, aluminium and other light elements

Abstract

The energy spectrum of 4.5 MeV protons scattered by some light elements was determined by using a proportional counter in conjunction with absorbing foils. Magnesium gave groups attributed to levels at 1.36 ± 0.03 and 1.82 ± 0.04 MeV respectively above the ground state, the former being almost certainly associated with 24 Mg. The angular distribution and excitation function of this group were examined in some detail. The proton groups from aluminium corresponded to levels at about 1 and 2.15 ± 0.05 MeV respectively above the ground state. The lower level has a complex structure and probably consists of two levels at about 0.80 and 0.97 ± 0.02 MeV, the amplitudes of the corresponding proton groups showing a marked angular dependence. No inelastically scattered protons were observed from carbon, oxygen, or copper, while beryllium gave a group consistent with the existence of a metastable state in 9 Be at 2.39 ± 0.05 MeV above the ground state. A short theoretical discussion of the mechanism of the process is given which suggests that inelastic scattering is predominantly a ( p, p ) process involving formation of a compound nucleus.