\begin{table}%t2  
\caption{\label{obsdata}Observational data.} 
\small%\centerline
{\begin{tabular}{lrllll}
\hline \hline 
                              & \multicolumn{1}{c}{Redshifted} &                            & \multicolumn{1}{c}{Time} &        \\ 
\multicolumn{1}{c}{Line} & \multicolumn{1}{c}{frequency}  & \multicolumn{1}{c}{Date} & \multicolumn{1}{c}{ON}     & \multicolumn{1}{c}{Array$^\diamond$}\\
                              & \multicolumn{1}{c}{(MHz)}      &                            & \multicolumn{1}{c}{source}      &           \\
\hline\noalign{\smallskip}
HCO$^+$ ($2\leftarrow 1$) & 94587.58 & 1999/06/11 & 3.0 h & 4C1  \\
              &          & 2001/03/20 & 2.5 h & 4ANT  \\
              &          & 2001/06/29 & 3.5 h & 4ANT \\
              &          & 2002/06/25 & 3.0 h & 5D  \\
              &          & 2003/02/26 & 2.2 h & 6Ap  \\
              &          & 2003/03/01 & 2.6 h & 6Ap   \\
\hline\noalign{\smallskip}
H$^{13}$CO$^+$ ($2\leftarrow 1$) & 92006.01 & 1999/06/13 & 2.9 h & 4C1  \\
                     &          & 2002/06/21 & 2.7 h & 5D   \\
                     &          & 2002/06/23 & 3.7 h & 5D  \\
                     &          & 2002/07/15 & 1.3 h & 5D   \\
\hline\noalign{\smallskip}
HC$^{18}$O$^+$ ($2\leftarrow 1$) & 90317.61 & 1999/08/03 & 3.2 h & 4ANT  \\
                     &          & 1999/09/09 & 2.8 h & 4C2  \\
                     &          & 1999/10/02 & 2.8 h & 4C2  \\
                     &          & 1999/11/12 & 1.8 h & 5D  \\
                     &          & 2001/05/08 & 1.7 h & 4ANT  \\
\hline\noalign{\smallskip}
HC$^{17}$O$^+$ ($2\leftarrow 1$) & 92327.67 & 1999/07/08 & 4.3 h & 4D2  \\
                     &          & 1999/07/15 & 3.7 h & 4D2  \\
                     &          & 1999/07/25 & 3.0 h & 4D2  \\
                     &          & 1999/09/24 & 2.0 h & 4C2  \\
                     &          & 1999/10/14 & 2.3 h & 4B1  \\
                     &          & 1999/10/26 & 2.0 h & 4B1  \\
                     &          & 1999/10/29 & 3.2 h & 4D1  \\
                     &          & 1999/11/01 & 3.2 h & 4D1  \\
                     &          & 1999/11/08 & 1.7 h & 5D   \\
\hline\noalign{\smallskip}
HCN ($2\leftarrow 1$) & 93996.83 & 1999/08/04 & 2.0 h & 4ANT  \\
          &          & 2003/08/03 & 1.3 h &  30M  \\
\hline\noalign{\smallskip}
H$^{13}$CN ($2\leftarrow 1$) & 91566.38 & 1999/08/29 & 2.7 h & 5D  \\
                 &          & 2001/07/03 & 2.6 h &  5D  \\
\hline\noalign{\smallskip}
HC$^{15}$N ($2\leftarrow 1$) & 91264.34 & 1999/08/25 & 4.2 h & 4D1  \\
                 &          & 1999/10/04 & 1.6 h & 4C2  \\
                 &          & 2001/05/28 & 2.0 h & 4ANT  \\
                 &          & 2001/05/30 & 1.5 h & 4ANT  \\
                 &          & 2001/08/13 & 3.3 h & 4D1  \\
                 &          & 2001/08/14 & 2.8 h & 4D1  \\
                 &          & 2001/08/15 & 3.7 h & 4D1  \\
\hline\noalign{\smallskip}
HNC ($2\leftarrow 1$) & 96151.68 & 2002/08/07 & 3.7 h & 5D  \\
\hline\noalign{\smallskip}
HN$^{13}$C ($2\leftarrow 1$) & 92362.69 & 2001/08/26 & 2.7 h & 4D1  \\
                 &          & 2001/10/15 & 1.2 h & 4ANT  \\
\hline\noalign{\smallskip}
H$^{15}$NC ($2\leftarrow 1$) & 94244.99 & 2001/08/04 & 2.8 h & 4D1  \\
                 &          & 2001/08/07 & 3.3 h & 4D1  \\
                 &          & 2001/08/25 & 2.7 h & 4D1  \\
\hline\noalign{\smallskip}
DNC ($2\leftarrow 1$) & 80924.89 & 2001/08/28 & 2.7 h & 4D1  \\
\hline\noalign{\smallskip}
CS ($4\leftarrow 3$) & 103909.33 & 1999/07/09 & 3.3 h & 4D2  \\
\hline\noalign{\smallskip}
C$^{34}$S ($4\leftarrow 3$) & 102246.49 & 1999/09/21 & 1.8 h & 4C2  \\
                &           & 1999/09/23 & 2.2 h & 4C2  \\
                &           & 2001/05/09 & 1.8 h & 3ANT  \\
                &           & 2001/05/10 & 3.4 h & 5D  \\
                &           & 2001/05/14 & 2.6 h & 5D  \\
\hline\noalign{\smallskip}
H$_2$S ($1_{10} \leftarrow 1_{01}$)$^\dagger$ & 89490.39 & 2005/07/05 & 4.3 h & 5D  \\
                           &          & 2005/07/29 & 3.2 h & 5D  \\
                           &          & 2005/09/05 & 3.0 h & 5D  \\
                           &          & 2005/09/09 & 1.8 h & 5D  \\
\hline 
\end{tabular}}
\smallskip
$^\diamond$ The number of antennae is given with the name of the array configuration if defined. \\
$^\dagger$ The H$_2^{34}$S (1$_{10} \leftarrow 1_{01}$) (89038.47 MHz) and H$_2^{33}$S (1$_{10}{-}1_{01}$) (89256.88~MHz) were observed simultaneously in the same correlator setup.
\end{table}