\begin{table}%t2
%\centering
\par
\newcommand{\T}{\rule{0pt}{2.6ex}}
\newcommand{\B}{\rule[-1.2ex]{0pt}{0pt}}
%\begin{center}
\par
\caption{Observed transitions.}
\label{transtab}
\begin{tabular}{lllccc}
\hline \hline
\multicolumn{2}{c}{Molecule} & Frequency & Transition & $E_l$ & $A_{ul}$ \\
Name & Chemical formula & (MHz) &            & (K)   & (s$^{-1}$) \\
\hline
\T Vinyl acetylene & C$_2$H$_3$~CCH & 90279.5 & 10$_{0,10}$ $\rightarrow$ 9$_{0,9}$ & 19 & $6.5\times 10^{-7}$ \\
 & & 90675.3 & 10$_{2,9}$ $\rightarrow$ 9$_{2,8}$ & 28 & $6.3\times 10^{-7}$ \\
 & & 90802.4 & 10$_{4,7/6}$ $\rightarrow$ 9$_{4,6/5}$ & 55 &
$ 1.1\times 10^{-6}$ \\
Amino acetonitrile & H$_2$N~CH$_2$~CN & 89768.0 & 10$_{0,10}$
 $\rightarrow$ 9$_{0,9}$ & 20 & $2.7\times 10^{-5}$ \\
 & & 90560.3 & 10$_{2,9}$ $\rightarrow$ 9$_{2,8}$ & 25 & $2.6\times 10^{-5}$ \\
Oxiranecarbonitrile & $c$-C$_3$H$_3$~NO & 89951.5 & 13$_{2,11}$
 $\rightarrow$ 12$_{2,10}$ & 37 & $3.5\times 10^{-5}$ \\
 & & 90493.7 & 13$_{1,12}$ $\rightarrow$ 12$_{1,11}$ & 36 &
 $3.0\times 10^{-5}$ \\ 
Vinyl cyanide & C$_2$H$_3$~CN & 103575.4 & 11$_{0,11}$ $\rightarrow$ 10$_{0,10}$ & 30 & $9.0\times 10^{-5}$ \\
 & & 104212.7 & 11$_{2,10}$ $\rightarrow$ 10$_{2,9}$& 39 & $8.9\times 10^{-5}$ \\
 & & 104419.3 & 11$_{6,5/6}$ $\rightarrow$ 10$_{6,4/5}$ & 108 & $6.5\times 10^{-5}$ \\
 & & 104432.8 & 11$_{3,9}$ $\rightarrow$ 10$_{3,8}$ & 50 & $8.5\times 10^{-5}$ \\
 & & 104437.5 & 11$_{7,4/5}$ $\rightarrow$ 10$_{7,3/4}$& 136 & $5.5\times 10^{-5}$ \\
 & & 104453.9 & 11$_{3,8}$ $\rightarrow$ 10$_{3,7}$ & 50 & $8.6\times 10^{-5}$ \\
\B & & 104461.5 & 11$_{8,3/4}$ $\rightarrow$ 10$_{8,2/3}$ & 168 & $4.4\times 10^{-5}$ \\
\hline
\end{tabular}
%\end{center}
\par
\end{table}