\begin{table}%t1
%\centering
\par
\tiny
\caption{\label{tab1}Spectroscopic parameters of the observed transitions.}
\begin{tabular}{rcrrrrr}
\hline\hline\rule[-3mm]{0mm}{6mm}
Transition & Frequency &  $E_l$            & $g_l$ & $g_u$ &$\mu^{2}S$\tablefootmark{a} & $10^{2}A_{ij}$  \\
                       &  ( MHz)            &  (cm$^{-1}$)  &            &              & ($\rm{D}^2$)                &     (s$^{-1}$)     \\
\hline
\multicolumn{7}{c}{\rule[-3mm]{0mm}{6mm} OH$^+$ $N=1{-}0$\tablefootmark{b} } \\
\multicolumn{7}{c}{\rule[-3mm]{0mm}{4mm} $J=1{-}0$} \\
$F=1/2{-}1/2$         &  $909045.2\pm1.5$   &  0.004  & 4 & 6 & 1.20  & 1.05 \\
    $ 1/2{-}3/2$         &  $909158.8\pm1.5$   &  0 & 2 & 4 &   2.40   & 0.52 \\
\multicolumn{7}{c}{\rule[-3mm]{0mm}{6mm} $J=2{-}1$} \\
$F=5/2{-}3/2$         &  $971803.8\pm1.5$   &  0  & 4 & 6 & 10.24  & 1.82 \\
    $ 3/2{-}1/2$         &  $971805.3\pm1.5$   &  0.004 & 2 & 4 &   5.69   & 1.52 \\
    $ 3/2{-}3/2$         &  $971919.2\pm1.0$   &  0 & 4 & 4 &   1.14   & 0.30 \\
\hline
\multicolumn{7}{c}{\rule[-3mm]{0mm}{6mm} o-H$_2$O$^+$  $1_{11}{-}0_{00}$\tablefootmark{c}} \\
%\hline
\multicolumn{7}{c}{\rule[-3mm]{0mm}{4mm} $J=3/2{-}1/2$} \\
$F=3/2{-}1/2$       & $1115150.0\pm1.8$    &  0.004 & 2 & 4 &   4.14  & 1.67 \\
     $1/2{-}1/2$       & $1115186.0\pm1.8$    &  0.004 & 2 & 2 &   3.32  & 2.68 \\
     $5/2{-}3/2$       & $1115204.0\pm1.8$    &  0 & 4 & 6 & 11.23  & 3.02 \\
     $3/2{-}3/2$       & $1115263.0\pm1.8$   &  0 & 4 & 4 &   3.35  & 1.35 \\
     $1/2{-}3/2$       & $1115298.7\pm1.8$   &  0 & 2 & 2 &   0.42  & 0.34 \\
\multicolumn{7}{c}{\rule[-3mm]{0mm}{6mm} $J=1/2{-}1/2$} \\
$F=3/2{-}1/2$       & $1139541.1\pm1.8$    &  0.004 & 2 & 2 &   0.42  & 3.61 \\
     $1/2{-}1/2$       & $1139560.6\pm1.8$    &  0.004 & 2 & 4 &   3.35  & 1.44 \\
     $5/2{-}3/2$       & $1139653.5\pm1.8$    &  0 & 4 & 2 &   3.32  & 2.86 \\
     $3/2{-}3/2$       & $1139673.3\pm1.8$   &  0 & 4 & 4 &    4.14  & 1.78 \\    
\hline
\multicolumn{7}{c}{\rule[-3mm]{0mm}{6mm}H$_3$O$^+$\tablefootmark{d} } \\
%\hline
$0_{0}^{-} {-} 1_{0}^{+}$  &   $984711.9\pm0.1$\tablefootmark{e}  &    5.1 &   4 & 12 & 8.30 & 2.30 \\
$1_{1}^{-} {-} 1_{1}^{+}$ & $1655834.8\pm0.3$\tablefootmark{f}  &    0 &   6 &   6 & 6.22 & 5.48 \\
$2_{2}^{-} {-} 2_{2}^{+}$  & $1657248.4\pm0.3$\tablefootmark{e} & 29.6  & 10 & 10 & 4.67 & 7.32 \\
\hline
\end{tabular}
\tablefoot {
\tablefoottext{a} {Dipole moments ($\mu$): 2.256~D (OH$^+$; Werner et~al.  \cite{Werner83}); 
2.37~D (H$_2$O$^+$; Wu et~al. \cite{Wu04}); 1.44~D (H$_3$O$^+$; Botschwina et~al.  \cite{Botschwina85}).} 
Frequencies from: \tablefoottext{b}{M{\"u}ller et~al. (\cite{Muller05}).} \tablefoottext{c}{M{\"u}rtz et~al. (\cite{Murtz98});} \tablefoottext{d}{Yu et~al. (\cite{Yu09}).}  
\tablefoottext{e}{$\int T_A {\rm d} v < 0.482$~K km s$^{-1}$ for the 984.7 GHz line, and 
$<$2.412~K~km~s$^{-1}$ for the 1657.2~GHz~lin.} 
\tablefoottext{f}{Blended with a strong $2_{12}{-}1_{10}$ {\it ortho}-H$_2^{18}$O~line at 1~655~831~MHz.}
}
\vspace*{-4mm}
\end{table}