\begin{table}%t1
%\centering
\par
\caption{\label{tab:spec}Frequencies of the H$_2$Cl$^+$ transitions observed.}
\begin{tabular}{rcccc}
\hline \hline \noalign{\smallskip}
 Transition & Frequency & Error & $A_{\rm ij}$  & $E_l$\\
&  ( MHz)      & (MHz)    &   (s$^{-1}$)     & (cm$^{-1}$)  \\
\hline
\multicolumn{5}{c}{\rule[-3mm]{0mm}{8mm}H$_2^{35}$Cl$^+$} \\
$1_{11}{-}0_{00}~3/2{-}3/2$   &  485413.427 &  0.029  & 0.00159 & 0 \\
$5/2-3/2$                        &  485417.670 &  0.015  & 0.00159 & 0 \\
$1/2-3/2$                        &  485420.796 &  0.057  & 0.00159 & 0\\
$2_{12}-1_{01}~5/2-5/2$    & 781609.303 & 0.063 & 0.00179 & 14.1\\
$3/2-1/2$                        & 781611.062  & 0.062 & 0.00248 &  14.1\\
$5/2-3/2$                        & 781622.721  & 0.063 & 0.00417 &  14.1\\
$7/2-5/2$                        & 781626.794  & 0.060 & 0.00596 &  14.1\\
$1/2-1/2$  &781628.554  & 0.061 & 0.00496 &  14.1\\
$3/2-3/2$  &781635.214  & 0.062 & 0.00318 &  14.1\\
\hline
\multicolumn{5}{c}{\rule[-3mm]{0mm}{8mm}H$_2^{37}$Cl$^+$} \\
$2_{12}-1_{01}~5/2-5/2$  & 780037.315  & 0.069 & 0.00178 &  14.1\\
$3/2-1/2$ &  780038.760  & 0.066 & 0.00247 &   14.1 \\
$5/2-3/2$ &  780047.903  & 0.066 & 0.00414 &   14.1 \\
$7/2-5/2$ &  780051.197  & 0.062 & 0.00592 &   14.1 \\
$1/2-1/2$ &  780052.642  & 0.065 & 0.00493 &   14.1 \\
$3/2-3/2$ &  780057.820  & 0.068 & 0.00316 &   14.1 \\
\hline
\end{tabular}
\tablefoot{Frequencies and spontaneous emission coefficients have been
calculated from the constants derived by Araki et~al. (\cite{araki01}), see also CDMS.}
\end{table}