  In this note, we prove Strichartz estimates for scattering states of scalar
charge transfer models in $\mathbb{R}^{3}$. Based on the idea of the proof of
Strichartz estimates which follows \cite{CM,RSS}, we also show the energy of
the whole evolution is bounded independently of time without using the phase
space method, for example, in \cite{Graf}. One can easily generalize our
argument to $\mathbb{R}^{n}$ for $n\geq3$. Finally, in the last section, we
discuss the extension of these results to matrix charge transfer models in
$\mathbb{R}^{3}$.
