Determination of Nuclear Reaction Mechanisms From Energy Spectra of Emitted Particles

Energy spectra of deuterons and tritons from ($p, d$) and ($p, t$) reactions are found to be peaked near their maximum energy, in contrast to the spectra of protons from ($d, p$) and ($t, p$) reactions which are peaked at low energy. It is shown that this characteristic of inverse reactions is to be expected from "stripping" and "pickup" reactions as a consequence of the fact that the former excite "particle" states while the latter excite "hole" states, but that it is not expected from collision type reaction mechanisms (e.g., "knockout"). It is thus concluded that ($t, p$) and ($p, t$) reactions as well as ($d, p$) and ($p, d$) reactions proceed by "stripping" and "pickup". The shape of energy spectra from ($p, \alpha$) and ($\alpha , p$) reactions indicates that the non-compound-nucleus portion of these also goes by "pickup" and "stripping"; there is corroboratory evidence for this from absolute cross sections.