Gamma-Ray Emission from Compound Nucleus Reactions of Helium and Carbon Ions

Abstract

The assumption that gamma emission does not occur in compound nucleus reactions until the excitation energy falls below the particle emission threshold was tested by direct observation of the gamma rays. Bombardments of Ba, Ho, Co, and Ta targets were carried out with helium ions; Te and V were bombarded with ${\mathrm{C}}^{12}$ ions. For the carbon ion reactions, in which the average angular momentum induced by the projectile ranged from $17\hslash$ to $38\hslash$, the total energy release in gamma rays exceeded the neutron binding energy, in contradiction to the assumption. This was not so for any alpha-particle reaction. A comparison of the gamma yields for the same compound nucleus, as produced by alpha particles and carbon ions at the same excitation energy, indicates that the enhancement is an angular momentum effect, independent of excitation energy.