Activation Cross-Section Survey of Deuteron-Induced Reactions

Abstract

A survey was made of activation cross sections for various nuclear reactions induced by 20-MeV deuterons. The ($d,p$) and ($d,t$) cross sections increase monotonically with increasing mass number, and in one case (${\mathrm{Ni}}^{58}$) the absolute ($d,p$) cross section is closely predicted by a distorted-wave Born approximation calculation. They are undoubtedly stripping and pickup reactions with little or no compound nucleus contribution. The fact that Coulomb barriers do not affect ($d,t$) cross sections indicates that the pickup occurs far outside the nucleus. The cross sections for ($d,2p$) reactions are consistent with a model wherein the second proton is "evaporated" from a compound nucleus, but the level density parameters needed to fit this theory are somewhat lower than expected; this may indicate a contribution from a mechanism in which both protons are emitted in a direct interaction. Excluding the lightest element studied, ${\mathrm{Cl}}^{35}$, the $(d,p\ensuremath{\alpha})+(d,\ensuremath{\alpha}p)$ activation cross sections are consistent with calculations assuming a reaction path that is predominantly ($d,p\ensuremath{\alpha}$) with evaporation of the second particle (i.e., one alpha) from a compound nucleus; however the reaction on ${\mathrm{Cl}}^{35}$ seems to proceed by the path ($d,\ensuremath{\alpha}p$) with both particles being evaporated. Cross sections for ($d,2n$) and ($d,n\ensuremath{\alpha}$) reactions in the mass range 60 to 90 indicate that many more low-energy neutrons than low-energy protons are emitted as first particles in deuteron-induced reactions; this indicates that compound nucleus formation is more important than stripping in these reactions.