\begin{table}%t2
\caption{\label{tab2}$\rm OH^+$ and $\rm H_2O^+$ abundances.}
%\centerline
{\small
\begin{tabular}{c c c c c c }
\hline\hline
$v_{\rm LSR}$ & $N({\rm H})$\tablefootmark{a} & ${\rm OH^+}$/H & ${\rm H_2O^+}$/H & $\zeta_{\rm H}\epsilon / n_2$ \\
$\rm km~s^{-1}$ & $10^{21}\rm cm^{-2}$ & & & $10^{-16}\rm s^{-1}$ \\
\hline\noalign{\smallskip}
30--50  &  6.95   &  $5.1 \times 10^{-8}$ & $ 5.1 \times 10^{-9}$ & 1.15 \\
50--78  &  7.23   &  $3.0 \times 10^{-8}$ & $ 2.6 \times 10^{-9}$ & 0.63 \\
\hline
\end{tabular}}
\tablefoot{\tablefoottext{a}{From Godard et~al.\ (\cite{Godard2010}) for an assumed spin temperature of 100~K.}}
\end{table}