https://doi.org/10.1351/goldbook.A00278
Radicals cations, $\ce{R3N^{.+}}$, derivable from aminium ions, $\ce{R3NH^{+}}$, by removal of a hydrogen atom. Aminiumyl radical ions are, except for $\ce{H3N^{.+}}$, synonymous with the ammoniumyl radical ions. As the term ammonium is well known, ammoniumyl radical ions is the more desirable class name.