Ambiguities in the inference of precompound emission from excitation function analysis

We address several indirect methods of deducing neutron emission energies in heavy ion reactions. It is shown that a pure statistical decay process can lead to apparently very high average neutron kinetic energies. It is shown that the result follows from prejudicial gating due to ignoring charged particle emission, and that the error is present even if only the $\mathrm{xn}$ channels are measured and analyzed. It is concluded that interpretation of experimental results vis-à-vis precompound particle emission must be performed with extreme caution when other than direct particle spectral measurements are performed.