\begin{table}%t2
%\centering
\par
\caption{Values of the critical impact parameter $b_0$ as a function
of the relative velocity $v$, as computed from Eq.~(\ref{b0}) for the {\caii}--{\hi} interaction.}\label{b0tab}
\begin{tabular}{lllll}
\hline\hline\noalign{\smallskip}
$v$ (km~s$^{-1}$) & 1 & 10 & 100 & 1000\\
\hline
$b_0$ (nm) & 0.785 & 0.24 & 0.078 & 0.024\\
\hline
\end{tabular}
\end{table}